Taxonomy of the Strawberry (Fragaria vesca Linneo, 1753) according to Cronquist System
Dominium/Domain: Eucaryotae Whittaker et Margulis, 1978
Kingdom: Plantae Haeckel, 1866
Subkingdom: Tracheobionta or Cormobionta (Vascular plants)
Superdivisio/Superdivision Spermatophyta (Seed plants)
Divisio/Division: Magnoliophyta (Flowering plants)
Classis/Class: Rosopsida Batsch, 1788
Subclassis/Subclass: Rosidae Takht., 1967
SuperOrdo/Superorder: Rosanae Takht., 1967
Ordo/Order: Rosales Bercht. & J.Presl, 1826
Subordo/Suborder: Rosineae Rchb., 1841
Familia/Family: Rosaceae Juss., 1789
Subfamilia/Subfamly: Fragarioideae A. Rich. ex Beilschm., 1833
Tribus/Tribe: Fragarieae Dumort., 1829
Subtribus/Subtribe: Fragariinae Torr. & A. Gray, 1840
Genus: Fragaria L. (1753)
Species: Fragaria vesca L. (1753)
Taxonomy of the Strawberry (Fragaria vesca Linneo, 1753) according to APG System
Ordo/Order: Rosales Bercht. & J.Presl, 1826
Subordo/Suborder: Rosineae Rchb., 1841
Familia/Family: Rosaceae Juss., 1789
Subfamilia/Subfamly: Fragarioideae A. Rich. ex Beilschm., 1833
Tribus/Tribe: Fragarieae Dumort., 1829
Subtribus/Subtribe: Fragariinae Torr. & A. Gray, 1840
Genus: Fragaria L. (1753)
Species: Fragaria vesca L. (1753)
Diffusion the strawberry in the world
The strawberry occupies, in the world, has a surface of 256 108 and from place to a production of 3,822,989 t. In Europe, the surface is about 177 378 and has the production of 1,449,385 t.
The cultivation of the strawberry is in the process of slow but progressive growth. Over a third of the area is concentrated in Eastern Europe, particularly in Poland (52,500 ha), Russia (38,000 ha) and Ukraine (11,200 ha). Significant investments are also recorded in the United States (22,000 ha), Germany (13,000 ha) and Turkey (10,000 ha).
The United States is the world's largest producer with an offer that exceeds 1.1 million tons, accounting for 35% of global production. Follows the Russian Federation, the protagonist of a considerable expansion of its production potential, the past over the past decade from 120 to 324 thousand tons per year, surpassing even Spain. The latter is in third place with an offer that, after several years of growth in 2007 does not exceed 263,000 tonnes. There has been strong increases in production also in other Mediterranean countries, such as Turkey (239,000 t), Egypt (104,000 t) and Morocco (100,000 t). Italy follows them with an offer for some years now in sharp decline in 2007 did not exceed 57,000 t, surpassed even by Great Britain in the same year produced 66,000 tonnes of strawberries. Even before are the productions of South Korea (200,000 tonnes), Japan (193,000 t), Poland (168,000 t), Mexico (160,000 tonnes) and Germany (153,000 t).
In Italy, the total area of strawberry was in 2007 to 6,033 ha, with a total production of 165 202 t and a yield of 27.25 t / ha. In 2008 there was a total area of 3,693 ha, with a total production of 65,372 t and a yield of 17.70 t / ha. It can be noted as, in Italy, the surface and the production yield of this crop has almost halved.
In Europe the cultivation of the strawberry is in the process of stagnation. The result to be approximately 170,000 hectares, of which largely localized in Eastern European countries joined the EU. The offer European Union in 2007 has settled down to around 1.5 million tonnes.
Spain, with a production of about 270,000 t, although lower, is consolidating its position as the leading producer countries of Europe. Poland, second largest producer of strawberries, has greatly expanded the cultivation in the first half of the last decade, then return to previous levels. The average yields in Poland continue to be much lower than those of Western Europe and South America and did not seem to show any increase. The total production capacity of the country is very large (168,000 t), distributed over an area of over 50,000 hectares.
In Italy the investments were practically halved in little more than 10 years, rising from 7,500 to 3,700 ha. For a long time the Italian strawberry cultivation is plagued by several problems: the difficulty of finding skilled labor, often unfavorable climatic conditions for the cultivation, earnings are not always sufficient to cover the costs of production, campaigns decidedly disappointing because of the frequent market crashes. Similar situation is found in France, where it currently detects an area planted amounted to 3,800 ha. Important areas planted with strawberries in Germany (13,000 ha) and the UK (4,000 ha).
The strawberry is a triangular red fruit, characterized by small dots, which we all well know for its intense and delicious flavour.
Actually, the strawberry is defined fruit improperly, because the actual fruits are the small dots on the strawberry, improperly called seeds.
Its origins are not well-defined: some sources claim that the strawberry is native to Europe and in particular to the area of Alps, while others consider the strawberry native to Chile, from where a French officer, in the early Eighteenth century, imported the mother plants in Europe, where they were used to create the hybrid Fragaria x ananassa, to whom all the varieties of strawberry currently available belong. The strawberry is a member of the rose family, with the most common varieties being a hybrid of the wild Virginia strawberry (native to North America) and a Chilean variety.
However, it seems that strawberries were already present on the tables of ancient Rome: the fruit was eaten during the celebrations in honour of Adonis. The legend says that when Adonis died, Venus shed copious tears, which, arriving on the Earth, were transformed into small red hearts: the fragrant strawberries.
According to other popular legends , more recent, but anyway lost in the mists of time, the strawberry would be able to protect from the bites of vipers and snakes: to avoid the dangerous poison of these animals, it is said that the leaves of this small plant should be collected on St. John's day. Therefore, people who collected the leaves on the 24th of June, essicated them and then made a braided belt, would have been protected from any possible bite, often fatal, of vipers and snakes. These are of course popular beliefs of the Italian peasant tradition, however these legends contribute to make strawberries even more extraordinary among all the fruits on our table.
Until the Seventeenth century, in Europe, native wild species Fragaria vesca, Fragaria viridis, or Fragaria moschata and other varieties of strawberry, brought from North America (Fragaria virginiana) were cultivated: in particular, with the introduction of the American species, the plant of strawberries produced much more large fruits.
The plant produces succulent, red, conical fruit from tiny white flowers, and sends out runners to propagate.
Although the plants can last 5 to 6 years with careful cultivation, most farmers use them as an annual crop, replanting yearly. Crops take 8 to 14 months to mature. Strawberries are social plants, requiring both a male and female to produce fruit.
The word strawberry comes from the Old English streawberige , most likely because the plant sends out runners which could be likened to pieces of straw. Although they have been around for thousands of years, strawberries were not actively cultivated until the Renaissance period in Europe.
Strawberries are native to North America, and the Indians used them in many dishes. The first colonists in America shipped the native larger strawberry plants back to Europe as early as 1600. Another variety was also discovered in Central and South America, which the conquistadors called "futilla". Early Americans did not bother cultivating strawberries, because they were abundant in the wilds.
Cultivation began in earnest in the early part of the 19th century, when strawberries with cream quickly became considered a luxurious dessert. New York became a strawberry hub with the advent of the railroad, shipping the crop in refrigerated railroad cars. Production spread to Arkansas, Louisiana, Florida and Tennessee. Now 75 percent of the North American crop is grown in California, and many areas have Strawberry Festivals, with the first one dating back to 1850.
The strawberry (Figure 1) is a perennial herbaceous plant, provided with stolons, that is of thin stems creeping along which, at the nodes, they develop roots, leaves and then flowers and fruits; nodes then you can get new plantlets.
Figure 1 - Botanical characteristics of the strawberry. Plant: a-plant mother, b-stem (rhizome), c-primary roots, d-secondary roots, e-stolon, f-plant stolon. Flower: g-petals, h-stamen, i-anthers of the stamens, l-the receptacle, m-sepals. Inflorescence: n- tertiary flower, o-quaternary flower, p-stem, q-peduncle, r-flower primary, s-bracts, t-secondary flower. Fruit: u-achenes (true fruit), v-sepals, z-receptacle.
The strawberry plant has a root system of type sorted, that is made up of primary and secondary roots. These extend in width to a radius of 25-30 cm and over and branching obliquely reaching a depth of a few tens of centimetres, variable depending on the type of soil and the availability of water.
In addition to performing the main function of anchoring and water absorption and of the nutritive elements, the root system also has the function of storing the reserve substances.
The stem is very short (2-3 cm) and takes the name of the rhizome; herbaceous consistency is when the plant is young and as you get older it becomes slightly woody.
The leaves, borne on petioles of variable length (from about 5 to 15 cm), are generally composed of three leaflets that have serrated edges characteristic for each variety, all fit on the same level and willing to fan (palmate leaves).
The inflorescences are "corymbs" (inflorescences in which the flowers are aligned at the same height, while the stalks depart from the main axis from different heights); the flowers are placed at the ends of stalks. In general, it is hermaphroditic flowers, which contain both the male organs i.e. (stamens bearing anthers with pollen), arranged around the receptacle, that the female (pistils, the base of which there are the ovaries containing the eggs), inserted into the receptacle. At the base of the flower is the chalice, consisting of green sepals (in number of 5 or more) which are outside the base of the corolla, that if constitued from petals (also in number of 5 or more) of white colour.
Pollination, that is the transport of pollen from the stamens to the top of the pistils (stigmas) is affidate to the wind (anemophilous pollination) or to the insects pollinators (pollinating insects).
The fruit is actually a "false fruit" as formed by the enlargement of the receptacle (indicated with the letter z of Figure 1) and takes the name of "sorosis", while the real fruits are achenes brownish green colour (those which generally are called seeds), which are inserted, more or less deeply, and in a variable number, on surface species of the false fruit. The shape of the fruit varies depending on the variety: it can be conical, conical-elongate, conical-rounded, conical-plate, truncated-conical, trapezoidal.
The colour can vary from orange to bright red to dark red.
Other distinctive features of the fruit are the size, the brilliance, the consistency of the pulp, the resistance of the surface to handling and the flavour (perfume, acidity and sweetness).
The Plant of Strawberries
The strawberry is a fruit characterized by an excellent aroma and a sweet taste.
The strawberry is a perennial stolonifera plant, consisting of a short stem, called peduncle or crown, on which grow sprouts and three long oval leaflets, serrated and arranged to form a small rose of leaves. The root system is shallow and it extends on a limited volume of soil, in fact, 90 % of roots are located in the first 15 cm of soil. At the axilla of leaves grow corymbs, consisting in 3-8 white flowers, which usually are self-fertile hermaphrodites; in case of flowers, the female varieties of strawberries need pollinators. The edible part of strawberries is the false fruit, resulting from the development of the receptacles, once fertilization occurred. The true fruits of strawberries are achenes, dry indehiscent fruits that remain attached to the fleshy false fruit. However, as we intend and eat strawberries, the fruit of the plant of strawberries is the edible part, characterized by a surface, covered with many yellow and brown small dots.
Although strawberries are cultivated from plains up to 1,000 meters above sea level, they require specific environmental conditions: best areas are those with a temperate climate, with short summers, characterized by hot periods, and winters cold enough. Strong summer solar heat, can in fact cause leaves to fall in advance, diebacks, dark and small misshaped fruits, with low consistency. During flowering, the plant of strawberries needs warm and uniform temperatures, while extreme changes in temperature between day and night and precipitations, contribute to hinder it.
For this reason, strawberries prefer loose, pH neutral or sub-acid soil, with a medium texture, fresh but well drained, with a depth exceeding 50 cm and rich in organic matter. Strawberries do not like heavy, asphyxiated, very calcarous and saline soils, with stagnant water, because in this case fruits become susceptible to gray mold.
The resistance to disease has become a more and more important aspect of the production of strawberries, as a result of climate change and events that have affected various areas cultivated with strawberries. In 2005, in fact, methyl bromide for fumigation of agricultural lands in industrialized countries, was abolished: to solve this problem, several researches have been started to find an alternative solution that will have a low environmental impact, among which there is the genetical improvements of strawberries, thanks to the identification of genotypes that show tolerance to diseases of the roots.
The most dangerous insects for strawberries, are aphides, which, because of the production of honeydew, cause sooty molt, rolling and curling of leaves and fruits, cutworms and othiorhyncus. To oppose pests, chemical intervention is suggested only if their presence in the field has crossed the threshold of damage, taking into account natural predators. Main fungi for the plant of strawberries are gray mold, powdery mildew or mildew, root rots, which occur in case of continuous cropping, anthracnose, brown rot and pitting.
The production of strawberries
The worldwide production of strawberries is attested around 2.5 million tons; the largest producers of strawberries are: the United States, with over 27.1% of the world production of strawberries, Spain, Japan, Italy, Russia and Korea.
Spain is the largest exporter of strawberries in Europe and second in world production, following the United States. Within the Spanish territory, the region of Huelva maintains the record with 90% of the production. In 2008/09, the area for the production of strawberries in this region amounted to 6,600 hectares, an increase over the preceding year: furthermore, in 2008/09, 66% of the area assigned to the production of strawberries was subject to the integrated production system. The production of strawberries in Spain reached 249,410 tons, of which 80% traded as fresh product.
In Italy, instead, the production of strawberries covers an area of approximately 6,000 hectares, which gives a production of strawberries of more than 130,000 tons. The record is due to the Italian region Campania, from which comes 31% of the national production (67,315 tons), followed by other regions such as Emilia-Romagna (15% amounting to 31,452 tons), Basilicata (14%), Veneto (12%), Piemonte (10%), Lazio (7%) and Sicily (2%).
Table 1 shows areas planted with strawberry per Region, divided in the open field and protected crops.
| Table 1 Areas planted with strawberries, in Italy, in 2007, divided into those involved in the open field and those relating to protected crops.
|| Open field
| Protected cultivation
Change on previous year
A growing number of producers of strawberries in italy is gearing up to tackle the difficult work necessary for the production of strawberries and the trade of strawberries. In spite of this, however, the Italian production of strawberries, compared to the the world production of strawberries covers a percentage of slightly more than 4.5%. The problem of strawberries quality is a highly considered matter of the production in any context, and especially in the fruit and vegetable trade, where consumption is generally stagnant. Researches show that on average, the quality characteristics of strawberries differentiated in the last ten years: this indicates that there has been a project for improving the production of strawberries, getting sweeter fruits. Therefore, if we act with genetics, or by monitoring the ways used for the cultivation of strawberries or by using a synergy of both, we can improve the quality of strawberries produced and distributed on the fruit and vegetable market.
The strawberry is certainly the crop, whose technics for the cultivation have more evolved and still are evolving in recent decades: the fast changes in "technologies" make the cultivation of strawberries get moved from an area, where some techniques are used, to another area, where new techniques are being introduced.
As mentioned before, Europe, Spain, Italy and France, are in order, the three main countries producers of strawberries. In recent years, in Belgium, Holland and in some areas of Italian Alps, there has been an expansion of the production of strawberries, with the development of "soilless" cultivation techniques, to produce "offseason" strawberries, to obtain early as well as delayed strawberries, compared to the usual strawberry season, which usually begins in December and ends in June.
The largest increases for the production of strawberries over the last ten years (2001-2011) were recorded in Turkey (+116%), in the former Soviet Union (+98%), in Spain (+78%), in Germany (+48%), in Korea (+42%), in the United States (+38%), in Mexico (+35%) and in Egypt (+25%). In the same period, several countries have reduced their production of strawberries: Poland (-26%), Japan (-22%), France (-22%), Italy (-6%) and Britain (-4%).
The world cultivation of strawberries has experienced significant and continuing growth on the fruit and vegetable market: large investments are recorded especcially in the Usa, Germany, Turkey and Spain, which has consolidated its role as the second largest world producer, with an offer that exceeds the threshold of 300,00 tons of strawberries produced.
The varieties of strawberries
In the realm of seasonal fruit, in particular in that of spring fruit, strawberry is the undisputed queen.
There are many species of varieties of strawberries, including: Fragaria chiloensis, from South America, Fragaria virginiana, native to the south of the United States and Fragaria ovalis, native to the Kurile Islands. All species of non-European origin are octoploid, while Fragaria vesca is diploid. The cultivated varieties are almost all crosses between Fragaria chiloensis and Fragaria virginiana.
In general, the plants of strawberries can be classified into:
Based on season of ripening, the varieties of strawberries are divided into:
- june-bearing or spring-bearing strawberries or short-days: buds form with less than 12 hours of daylight and with a sufficient temperature range. Buds form from September up to the first frosts and fruits ripe in spring during about 4 weeks. Some june-bearing varieties can, sometimes become ever-bearing.
- ever-bearing or long-days:buds form with more than 14 hours of daylight and produce strawberries from Sring to Fall. They have never been widespread at industrial level, but are used almost exclusively in families for their slowness in breeding: they produce few runners and multiply mainly by plant division;
- day neutral : buds form under any daylight condition, as long as the temperature range is observed.
Starting from early strawberries to the late season, some varieties of strawberries are: "Alba", "Queen Elisa", "Clery", "Irma", "Adria", "Record Argentera" and "Sveva".
- early season,
- late midsesason and
- late season.
In the south of Italy the most important varieties are: "Ventana", "Nora", "Kilo", "Camarosa" and "Candonga Sabrosa".
Strawberries prefer temperate climate and a good exposure to sun: they grow wild in woods, brush and fresh places all over peninsular Italy, but they can easily be cultivated. For botanists, strawberries are not exactly fruits, but rather a kind of weed, and in Europe three spontaneous species of strawberries are known: vesca, moscata and viridis.
The spontaneous variety of strawberries, vesca, is formed by a bush, which can be 10 up to 30 cm tall, with trifoliate, toothed leaves: the plants of strawberries belonging to this variety are usually dark green on the upper side of leaves and silver-grey on the lower side. Flowers of strawberries, grouped in 5-8, have always five white petals with many stamens. The runners (stolons) produce radicles that give birth to new seedlings.
This variety of strawberris is better known as woodland strawberry, just because it grows wild especially in woods of mountain environments: it is characterized by small and fragrant fruits, which are harvested from June to Semptember; this variety of strawberry is cultivated above all in the Italian region Trentino.
Strawberries ripe from May to July, according to the areas in which they are cultivated, however, technically, real fruits are those tiny grains on receptacle, while the short hair among them is the rest of pistils.
Less widespread are instead: the variety of strawberry Fragaria moscata, recognisable from erected and quite tall flowering stems, which grow above leaves ad small pear-shaped fruits at the base, and the variety of Fragaria viridis, with short flowering stems, leaves bright as silk and smaller fruits.
Strawberries are extolled as spring seasonal fruit and for their nutritional, refreshing, astringent, diuretic, antigottose properties and their beneficial depurative action on blood. Rich in vitamin A, B1, B2 and C, sugars, phosphorus, calcium, iron, flavoinoids and salicylic acid, the strawberry is a very valuable fresh fruit, even though it can cause allergy in predisposed people: in fact, strawberries are usually not recommended to patients already suffering from eczeme and hives, to diabetics, obese people and dispeptics. Many virtues are assigned to strawberries and they can be helpful in curing some deseases, such as rheumatisms and high blood pressure, because they stimulate the production of hormones that regulate the nervous system. Strawberries have a refreshing, depurative ad duretic action on the organism, thanks to the presence of potassium. Furthermore, strawberries are a dietic fruit, as they are low in calories: 100 gr of strawberries contain only 24 kcal and they are also low in minerals.
The most cultivated species, Fragaria x ananassa, comes froms several crosses between Fragaria chiloensis and Fragaria virginiana.
Presently, there is a progressive increase in the acreage of strawberries cultivated in greenhouse-tunnel and a parallel decrease in open field cultivation, even though early productions are not required: this choice is motivated by the fact that farmers want to avoid the risk of damage due to bad weather, given the great investment that this cultivation involves and harvesting periods always at risk of rain, hail, frost.
Moreover, new techniques for the cultivation of strawberries and "offseason" production, were recently developed: these cultivation require a different kind of "enlarged plants".
"Enlarged plants" are used in "offseason" cultivation, both for fall productions, and for summer mountain production, as they are able to produce a sufficient number of flowers to ensure a good production already after 50-70 days from plantation. They are also the only plants that can be used in the "soilless" cultivation, a technique developed in Belgium and Holland that is cosidered more and more interesting also in Italy, where is sometimes applied. It is a very sophisticate and expensive technique that consists in cultivating the plants of strawberries in bags of fertilized peat, placed on supports at 1.20 to 1.50 m from the soil in greenhouses with irrigation systems.
"Enlarged plants" allow two production cycles, the first at 60-70 days after transplanting and the second, normal in Spring.
Varieties of strawberries that can be stored in refrigerators or cultivate fresh include:
The necessity to improve strawberries characteristics has pushed private farmers and institutions to actuate importat breeding programms, in order to find new varieties. Since 1980, this activity has become increasingly intense and now involves 40 countries, of which 35 have found new varieties. As a whole 750 varieties of strawberries have been created: they mainly belong to the species Fragaria x ananassa and only minimally to the decaploid species Fragaria x potentilla and Fragaria vesca.
- Strawberries waiting bed (WB): plants stored in refrigerators after an enlargement done in beds with 2 or more buds per flower.
- Strawberries trayplant (TP): plants stored in refrigerators with part of the flowers obtained by runners that had radicated and afterwards enlarged in special receptacles and in protected environments.
- Strawberries A+ : plants stored in refrigerator selected with a calibre higher than 14 mm.
- Strawberries with rooted tops: fresh plants derived from young runners, with small roots, rooted in polystyrene trays, with 50-80 alveoli and sold ready for transplant.
- Strawberry plants in pots: fresh plants that may have originated from plants of small diameters (AA) stored in refrigerators or from fresh runners more or less rooted and put in plastic pots to complete rooting. Fresh plants rooted in pots permit to anticipate the plantation of about one month compared to the fresh Spanish plants, done in the South of Italy, with undoubtful advantages as to increase in the production and earlyness of the fresh plant has compared to the one stored in refrigerators.
- Antea strawberries: Early midseason variety that suits to any European environment. Fruits, regular and alongated, are homogeneous, attractive, bright red also when completely ripe. Flesh and skin are very resistant to manipulations and to the transport. Variety characterized by excellent trading and gastronomic qualities.
- Candonga strawberries: Variety selected in Spain. It is a very rustic and vigorous plant. It suits well to organic and integrated cultivation. This variety differs from the others for its organoleptic characteristics. The fruit is medium-large, cone shaped and bright red. The flesh is red, compact and very sugary. The skin id very resistant to harvesting and transport. Very interesting cultivation for its good and constant productivity during all the period of harvesting.
- Chiflona strawberries: Selected in Spain, is a popular variety for its earlyness that allows to obtain a good production in the early months of the season, It's a plant of medium vigour. The fruits are wedged cone-shaped and bright red. The fruit size is medium-large and it is constant until the end of harvesting. The flesh is homogeneous and red, aromatic and slightly acid. The skin is elastic and resistant to damage from handling and transport. It suits to Mediterranean environments and it is not sensitive to changes in climate.
- Clery strawberries: Very early variety that suits to European temperate environments. It is characterized by excellent productivity, trading and organoleptic qualities. The fruit is bright crimson red, cone shaped, regular already in the first harvestings. Organoleptic qualities are high, as well as taste characteristic of aroma and intense flavour. Excellent resistance to handling and transports.
- Cristal hidrop strawberries: Ever bearing variety that has a high production level and that suits very well to areas perfect for strawberries and is particularly suitable for the fall and winter production. Fruits are bright red, with a compact, sugary and aromatic flesh. Cristal is a patented variety and reproduction without authorization from Planasa S.A. is forbidden.
- Elsegarde® strawberries civr 30: It is an everbearing variety that suits well to European continental environments, with a constant production throughout all the growing season. The fruit is very attractive, cone shaped, large sized, bright red and with excellent organoleptic characteristics.
- Elsinore® strawberries civr 30: Fruit with the form of a cone or a truncated cone, large sized and with a red-orange uniform colour.The flesh is red, firm and good tasting. It is an everbearing variety that suits well to continental environments and that, for its excellent organoleptic and aesthetical characteristics, is one of the most interesting varieties on the market.
- Dely* strawberries: Recently introducted, it is an early variety that suits to continenatl areas. Its fruits are good-sized, bright red and have a high "brix" degree. Taste, flavour and fragrance are inspired to woodland strawberries, being for this reason at the top of gastronomic qualities.
- Joly* strawberries: It is a late midseason variety, very productive and suitable to continental areas. Recently introduced, it has a cone ore truncated cone shape, a big size, which remains homogeneous throughout all the harvesting period. The flesh has the same colour of the skin and taste is very sweet, with a delicious aroma and excellent organoleptic qualities.
- Naiad® strawberries civr 35: Early mid season variety, with a great productivity level. The fruits are attractive, tasty and are quite resistat thanks to the texture of their flesh. The fruits have the shape of an alongated cone and are medium/big sized and uniform, their skin is intense red and their flesh, also red is really tasty.
- Siba* strawberries: Early season variety with a good productivity level, whose fruits have the shape of an alongated cone and are big-sized, they are very attractive, bright red and have a great texture. The flesh, intense red, is very sweet, has a good flavour and is really tasty.
- Tudnew® strawberries: Variety selected in Spain and cultivated in areas with a Mediterranean climate, both as a plant stored in refrigerators or fresh. It is a very interesting variety for its great productivity level and the exellent quality of its fruits. Fruits are cone shaped and of a big size that remains the same for the entire season. The bright red skin of fruits has a great resistance to harvesting and to transport. The flesh, also bright red is compact, tasty and has an excellent flavour. These characteristics fulfill the requirements of Italian and foreign markets.
- Chandler strawberries: variety, whose fruits are cone shaped and a bit flat; they are cultivated in Sicily, but are native to California. The flesh is red and has a good flavour and fruits are particularly resistant to transport.
- Miranda strawberries: native to Italy, this variety grows in the Centre and south of Italy. The fruits are red-orange and are very big.
- Pajaro® strawberries: this variety is native to California and can be cultivated only with authorization. The plant is very vigorous and productive and fruits are big and bright red. Their size and qualtity remains steady throughout the period of harvesting.
- Tudla® strawberries: native to Spain, this variety is cultivated also in Italy with specific authorization. It is a very early season variety, fruits are incredibly big, red verging to dark red and very juicy; it is produced mainly in Sicily.
- Idea strawberries: plants become very big, vigorous and thick. Its fruits are sweet and the flesh is red-orange. It is cultivated in the North of Italy and is the most late season variety among those there cultivated.
The main genetic improvement programs are concentrated in North America (35 programs, of which 13 private), in the Europe Union (34 programs, of which 16 private), in the non-EU countries (17 program of which 2 private) and in Asia (19 program of which 1 private), for a total of 79 public programs and 32 private.
Starting from the mid-Nineties on, the quantity of varieties of strawberies doubled compared to the previous 15 years: this is due to the intense genetic improvement activity of privates, who until that moment were not active compared to the public institutions. Several genetic improvement programs had a great success in the last two decades. This allowed the diffusion of varieties that have a great adaptability to different environments and completely fulfill the requirements of producers and consumers all over the world. For example, the program of the University of California (UC) that produced a lot of successful varieties, such as "Camarosa", "Chandler", "Seascape" and "Pajaro". Altogether, the UC varieties represent more than 50% of the surface assigned to the production of strawberries in the world. Private genetic improvement programs had more and more impulse: these programs aim at being financed with the royalties given by patents.
Nurserymen of strawberries
The production of the fruit plants is parallel to the trade of fruit: today's consumers, much more than before, demand quality in the fruit they purchase.
Fruit growers and producers of strawberries, nowadays understand that the success of a cultivation largely depends on the quality of the material used, on the plants of strawberries sown: the extrinsic qualities, such as development, the number of branches, the graft, but also the intrinsic qualities of the plants of strawberries, such as the health of materials, the genetic certainty, the compatibility between plants arranged with flower buds already differentiated (for fast set-fruit) and grafts taken from mother plants, carefully controlled and kept, in order to retain the best features of the original clone.
The accuracy toward these characteristics makes the plants of strawberries produced of a high and superior quality, even though, in parallel, this factor has often an effect also on the costs for the consumer.
The high costs for the cultivation today do not allow basic errors by nurserymen of strawberries and by fruit growers in general: it is useless to prepare well the ground, fertlize, provide an irrigation system and pile driving, if the plants do not meet best quality requirements.
Nowadays, for nurserymen of strawberries, plant certification is a guarantee of high standards of quality and health: it is not sufficient to resolve all the problems that arise in the production of strawberries, but, in fruits, the lack of conditions that can compromise the quality and quantity of the production of strawberries is definitely essential for the succes of the cultivation.
Recently, it has developed in the world fruit and vegetable sector, the tendency to produce strawberries in nurseries: building repository of basic materials, "thermotherapy" cells, "isolation greenhouses", fields of mother plants, centres for the meristematic multiplication for the production of strawberries are just some of the steps for the production of strawberries in nurseries. The results are fruits from certified plants free from viruses.
In Italy, already in the early Eighties, the region Emilia Romagna, began the procedures for the voluntary certification of fruit plants and strawberry plants; in the meantime began its activities the C.A.V., (Centro Attivita Vivaistiche - Nursery Activity Centre), the interprofessional body responsible for carrying out, together with the regional O.M.P. (Osservatorio per le Malattie delle Piante -Observatory for Plant Diseases), the entire process of voluntary certification of fruit plants. Finally, in the Nineties, the multiple needs of the nursery sector and of the entire Italian fruit and vegetable sector prompted government authorities to seek a cooperative relationship with CIVITALIA, interprofessional body, specially created by major nurserymen organizations (also nurserymen of strawberries) and by fruit and vegetable producers, to start the "national certification of fruit plants" for a long time advocated, in order to put the national nursery at par with that of the other Eu countries producing certfied fruit and vegetables.
In Italy, in the sector of strawberries, the production of certified plants has shown a steady increase, thanks to the continuous introduction of new varieties and new grafts: from the point of view of nursery, a growth path, in terms of cultivated area (approximately 500 HA) and quatities produced, has been embarked.
Obtaining licenses to propagate varieties, patented by the most important sources of research and testing worldwide, has also led to compliance with specific duties and conduct in keeping with international rules to which Italy has adhered with some delay.
This membership, however, has allowed agreements to have the exclusive right for the most famous varieties of strawberries obtained from the University of California, still today of global importance, as well as for many other varieties of strawberries.
The varieties of strawberries suitable for the nursery include a very broad spectrum.
For the production of strawberries in nurseries, nurserymen use above these varieties:
The varieties of strawberries in the U.S.A.
- "Anita": junebearing variety of strawberries, with good levels of production, good flesh tesxture and a high refraptometric grade. Alone represents 50% of the junebearing plants of strawberries produced.
- "Splendor": new variety of strawberries, resulting from the program for the development of varieties of Plant Sciences & Berry Genetics; this particolar variety of strawberries was chosen in the testing fields of Spain and California among a great number of selections. It is a junebearing, short-day variety; its cultivation suits very well to the Mediterranean climate: the South of Spain and of Italy, the south of Greece and the North of Marocco are therefore ideal areas for the production of this variety of strawberries.
Many people come in USA looking for advice on which specific strawberry variety they should plant in their respective states. Well, as one might expect, there are a lot of different climates and growing conditions out there. Each of the United States has its own unique general soil composition, rainfall, and weather patterns.
Consequently, any given strawberry plant variety is likely to do better in one specific region than other regions. While some cultivars are able to adapt to many environments, others have been bred to be highly productive in a relatively narrow climate range.
This guide is a state-by-state list of strawberry varieties that do well in each state. Once you find your state and a prospective variety for your own garden, you can check the Strawberry Varieties page for more information. Here are the recommended strawberry varieties for each state.
The states and the specific varieties recommended for growing in each one are listed in alphabetical order below.
The trade of strawberries
- Alabama: "Albritton"", "Allstar", "Cardinal", "Chandler"", "Delite", "Douglas", "Earlibelle", "Earliglow", "Sunrise". (According to the Alabama Cooperative Extension Services of Alabama A&M and Auburn Universities).
- Alaska: "Brighton", "Fern", "Hecker", "Irvine", "Mrak", "Muir", "Ogallala", "Ozark Beauty", "Quinault", "Selva", "Streamliner", "Superfection", "Tillicum", "Tribute", "Tristar", "Yolo. (According to the University of Alaska Fairbanks Cooperative Extension Service).
- Arizona: "Camarosa", "Chandler. Note: "Arizona is not considered a good location for strawberry cultivation. (According to the University of Arizona Citrus Agricultural Center).
- Arkansas: "Cardinal", "Camarosa", "Chandler", "Delmarvel", "Earliglow", "Lateglow", "Noreaster", "Sweet Charlie", "Tribute", "Tristar. (According to the University of Arkansas Department of Agriculture Cooperative Extension Service).
- California: "Albion", "Aromas", "Camarosa", "Camino Real", "Chandler", "Diamante", "Gaviota", "Oso Grande", "Pacific", "Seascape", "Selva", "Ventana. (According to the California Strawberry Commission).
- Colorado: "Catskill", "Empire", "Fairfax", "Fort Laramie", "Geneva", "Guardian", "Marlate", "Ogallala", "Ozark Beauty", "Quinault", "Redchief", "Red Rich", "Redstar", "Robinson", "Superfection", "Tribute. (Colorado State University Cooperative Extension Service).
- Connecticut: "Brunswick", "Cabot", "Clancy", "Darselect", "Earliglow", "Eros", "Honeoye", "Jewel", "LAmour", "Sable. (According to the New England Vegetable and Fruit Conference).
Delaware: "Allstar", "Delite", "Earliglow", "Guardian", "Late Glow", "Red Chief", "Sparkle", "Tribute", "Tristar. (According to the University of Delaware College of Agriculture & Natural Resources Cooperative Extension).
Florida: "Calibrate", "Camarosa", "Florida Belle", "Florida 90", "Rosa Linda", "Sequoia", "Sweet Charlie", "Strawberry Festival", "Tioga. (According to the University of Florida University Relations Department).
Georgia: "Apollo", "Delite", "Cardinal", "Earliglow", "Sunrise", "Surecrop. (According to the University of Georgia College of Agricultural & Environmental Sciences).
- Hawaii: "Eversweet", "Quinault", "Seascape. Although strawberries are grown commercially on the Islands", "and the Fragaria chiloensis species of strawberries grow at elevation there", "they are more difficult to grow in the tropical environment and not highly recommended. The three varieties listed are sold in nurseries on Hawaii.
Idaho: "Allstar", "Benton", "Blomidon", "Catskill", "Cavendish", "Earliglow", "Fort Laramie", "Glooscap", "Guardian", "Honeoye", "Jewel", "Lateglow", "Lester", "Micmac", "Quinault", "Redchief", "Scott", "Shuksan", "Surecrop", "Totem", "Tribute", "Tristar. (According to the University of Idaho Extension Service).
Illinois: "Allstar", "Annapolis", "Delmarvel", "Earliglow", "Honeoye", "Jewel", "Kent", "Seneca", "Tribute", "Tristar. (According to the University of Illinois Extension Service).
Indiana: "Delite", "Earliglow", "Fort Laramie", "Guardian", "Sunrise", "Ozark Beauty", "Redchief", "Sparkle", "Surecrop. (According to the Purdue University Extension Service).
Iowa: "Annapolis", "Cavendish", "Delmarvel", "Honeoye", "Jewel", "Kent", "Mohawk", "Primetime", "Winona. (According to the Iowa State University Southeast Research and Demonstration Farm).
Kansas: "Allstar", "Earliglow", "Guardian", "Northeaster", "Ogallala", "Ozark Beauty", "Primetime", "Redchief", "Tribute", "Tristar. (According to the Kansas State University Agricultural Experiment Station and Cooperative Extension Services Horticultural Report).
Kentucky: "Camarosa", "Chandler", "Jewel", "Northeaster", "Sweet Charlie. (According to the University of Kentucky Department of Horticulture and Landscape Architectures Fruit and Vegetable Crops Research Report).
Louisiana: "Camarosa", "Camino Real", "Strawberry Festival. (According to the Louisiana State University AgCenter Research & Extension).
Maine: "Allstar", "Bounty", "Catskill", "Earliglow", "Guardian", "Lateglow", "Midway", "Mira", "Mohawk", "Northeaster", "Surecrop. (According to the University of Maine Cooperative Extension Service).
Maryland: "Allstar", "Bish", "Chandler", "Darselect", "Eros", "Jewel", "KRS-10", "Oviation", "Seascape. (According to the University of Maryland Agricultural Experiment Station).
- . Flavorfest (recommended by Kim Lewers of the USDAs Agricultural Research Service).
Massachusetts: "Catskill", "Earlidawn", "Fletcher", "Guardian", "Midway", "Raritan", "Redchief", "Sparkle", "Surecrop. (According to farminfo.org).
Michigan: "Allstar", "Annapolis", "Bounty", "Cavendish", "Chambly", "Delmarvel", "Earliglow", "Glooscap", "Honeoye", "Jewel", "Redchief", "Tribute", "Tristar. (According to the Michigan State University Extension Van Buren County).
Minnesota: "Cavendish", "Kent", "Mesabi", "Winona. (According to the University of Minnesota Agricultural Experiment Station and Extension Service).
Mississippi: "Cardinal", "Chandler", "Comet", "Dixieland", "Douglas", "Florida 90", "Pocahontas", "Sunrise", "Tangi", "Tennessee Beauty. (According to the Mississippi State University Extension Service).
Missouri: "Allstar", "Cardinal", "Earliglow", "Guardian", "Honeoye", "Jewel", "Lateglow", "Ogallala", "Ozark Beauty", "Redchief", "Sparkle", "Surecrop", "Tribute", "Tristar. (According to the University of Missouri Horticultural MU Guide).
Montana: "Catskill", "Fern", "Fort Laramie", "Gem", "Glooscap", "Hecker", "Honeoye", "Ogallala", "Red Rich", "Redcoat", "Senator Dunlap", "Sparkle", "Streamliner", "Tribute", "Tristar", "Veestar", "Vibrant. (According to the Montana State University Extension Service).
Nebraska: "Earliglow", "Ft. Laramie", "Ogallala", "Sunrise", "Surecrop", "Redchief", "Tribute", "Tristar. (According to the University of Nebraska Lincoln Extension in Lancaster County).
Nevada: "Camarosa", "Chandler. Note: "Nevada is not considered a good location for strawberry traditional strawberry cultivation.
New Hampshire: "Allstar", "Cavendish", "Cornwallis", "Earliglow", "Redchief", "Sparkle. (According to the University of New Hampshire Cooperative Extension).
New Jersey: "Delmarvel", "Earliglow", "Guardian", "Latestar", "Lester", "Northeaster", "Raritan", "Redchief", "Sparkle", "Tribute", "Tristar. (According to the National Sustainable Agriculture Information Service).
New Mexico: "Fern", "Fort Laramie", "Gem", "Guardian", "Ogallala", "Ozark Beauty", "Quinault", "Robinson", "Selva", "Sequoia", "Streamliner", "Superfection", "Surecrop", "Tribute", "Tristar", "Tufts. (According to the New Mexico State University Cooperative Extension Service and College of Agriculture and Home Economics).
New York: "Allstar", "Bounty", "Cavendish", "Delite", "Earliglow", "Fletcher", "Guardian", "Honeoye", "Jewel", "Kent", "Raritan", "Redchief", "Scott. (According to the Cornell Cooperative Extension Suffolk County).
North Carolina: "Albion", "Bish", "Camarosa", "Camino Real", "Chandler", "Gaviota", "Gem Star", "Oso Grande", "Seascape", "Strawberry Festival", "Sweet Charlie", "Treasure", "Ventana. (According to the North Carolina Strawberry Association).
North Dakota: "Dunlap", "Ft. Laramie", "Gem", "Honeoye", "Redcoat", "Stoplight", "Trumpeter. (According to the North Dakota State Agricultural and University Extension).
Ohio: "Delite", "Earliglow", "Guardian", "Kent", "Lateglow", "Lester", "Midway", "Redchief", "Surecrop", "Tribute", "Tristar. (According to the Ohio State University Extension).
Oklahoma: "Albritton ", "Allstar", "Apollo", "Arking", "Blakemore", "Canoga", "Cardinal", "Chandler", "Delite", "Earliglow", "Fletcher", "Guardian", "Holiday", "Hood", "Lateglow", "Luscious Lady", "Ozark Beauty", "Scott", "Spring Giant", "Sunrise", "Surecrop", "Tennessee Beauty", "Trumpeter. (According to the Oklahoma State University Cooperative Extension Service).
Oregon: "Benton", "Fern", "Ft. Laramie", "Hecker", "Hood", "Olympus", "Ozark Beauty", "Puget Reliance", "Quinault", "Rainier", "Redcrest", "Selva", "Shuksan", "Sumas", "Tillikum", "Tristar", "Totem. (According to the Oregon State University Extension Service).
Pennsylvania: "Albion", "Allstar", "Camarosa", "Chandler", "Darselect", "Earliglow", "Everest", "Evie-2", "Honeoye", "Jewel", "LAmour", "Seascape", "Sweet Charlie", "Tribute", "Tristar", "Wendy. (According to the Penn State University Small-scale and Part-time Farming Project).
Rhode Island: "Brunswick", "Cabot", "Clancy", "Darselect", "Earliglow", "Eros", "Honeoye", "Jewel", "LAmour", "Sable. (According to the New England Vegetable and Fruit Conference).
South Carolina: "Albritton", "Apollo", "Cardinal", "Chandler", "Delite", "Douglas", "Earliglow", "Florida 90", "Sunrise", "Surecrop", "Tioga. (According to the Clemson University Cooperative Extension Service).
South Dakota: "Annapolis", "Bounty", "Crimson King", "Earliglow", "Ft. Laramie", "Glooscap", "Honeoye", "Jewel", "Kent", "Ogallala", "Ozark Beauty", "Redcoat", "Selva", "Seneca", "Settler", "Sparkle", "Tribute", "Tristar", "Trumpeter", "Veestar. (According to the South Dakota State University Cooperative Extension Service).
Tennessee: "Allstar", "Cardinal", "Delite", "Delmarvel", "Earliglow", "Guardian", "Lateglow", "Red Chief", "Scott", "Surecrop", "Tribute", "Tristar. (According to the Agricultural Extension Service of the University of Tennessee).
Texas: "Allstar", "Cardinal", "Chandler", "Douglas", "Pajaro", "Sequoia. (According to the Texas A&M System", "Department of Horticultural Sciences", "AgriLife Extension).
Utah: "Allstar", "Chandler", "Earliglow", "Evie-2", "Honeoye", "Jewel", "Ogallala", "Seascape", "Sparkle", "Tribute. (According to the Utah State University Cooperative Extension).
Vermont: "Allstar", "Annapolis", "Brunswick", "Cabot", "Cavendish", "Clancey", "Cornwallis", "Darselect", "Earliglow", "Everest", "Honeoye", "Jewel", "Kent", "LAmour", "Lateglow", "Mesabi", "Mic Mac", "Mira", "Mohawk", "Northeaster", "Sable", "Seascape", "Seneca", "Sparkle", "Tribute", "Tristar", "Veestar", "Winona. (According to the University of Vermont Extension).
Virginia: "Allstar", "Delite", "Delmarvel", "Earliglow", "Honeoye", "Lateglow", "Ozark Beauty", "Redchief", "Sunrise", "Surecrop", "Tribute", "Tristar. (According to the Virginia Cooperative Extension).
Washington: "Hood", "Nanaimo", "Puget Reliance", "Quinault", "Rainier", "Selva", "Shuksan", "Tillicum", "Totem", "Tribute", "Tristar. (According to the Washington State University Extension).
West Virginia: "Allstar", "Annapolis", "Earliglow", "Sable", "Seneca", "Surecrop. (According to the West Virginia University Extension Service).
Wisconsin: "Annapolis", "Cavendish", "Crimson Fern", "Fort Laramie", "King", "Earliglow", "Glooscap", "Honeoye", "Jewel", "Kent", "Lateglow", "Lester", "Mesabi", "Mira", "Ogallala", "Ozark Beauty", "Raritan", "Redchief", "Seascape", "Selva", "Seneca", "Sparkle", "Tribute", "Tristar", "Winona. (According to the Cooperative Extension System of the University of Wisconsin).
Wyoming: "Dunlap", "Fort Laramie", "Guardian", "Honeoye", "Ogallala", "Ozark Beauty", "Quinault", "Redcoat", "Surecrop", "Tribute", "Tristar", "Trumpeter. (According to the University of Wyoming College of Agriculture).
The export of strawberries on the international fruit and vegetable market is increasing (data from 2011): in fact, the total value of exported strawberries is just over 43 million euros, with an increase of 13%. About 80% of the production of strawberries is directed to Eu countries, with particular reference to Germany (over 50%) and Austria (more than 14%).
As regard the Italian import of strawberries, the presence of foreign products is steadily increasing. Strawberries consumed in Italy, are mainly from Spain, 63%, and from France, 28%,. Imports of strawberries from extra EU areas and from countries of North Africa, are being recorded, even though they are not yet significant, even representing booming countries with relevant prospectives.
The main destination of strawberries from Spain, world's second larger producer of strawberries and EU first exporter of strawberries, with 228,584 tons of strawberries exported in 2011, are the European countries, in particular France and Germany, which absorb 63% of the total volume exported. Exportations in 2009 increased significantly compared to the preceding year.
In value terms, exports in 2011 totalled 437 million euros, 11% more than 2010. The French exports during the same period, instead, totalled 15,155 tons, while the Italian exports were of 14,857 tons. A more and more increasing portion of the Spanish production of strawberries is represented by indigenous varieties developed by the same Spanish producers from the Huelva region, who have begun to replace the varieties from the United States.
In France, instead, a strong growth of soiless cultivation of strawberries, has been recorded, representing 40% of the production resulting from producers organizations (OP).
More generally, there has been an increase in the production in other European countries, such as Germany and the United Kingdom, and in non-EU countries, such as Marocco and Egypt.
Also with regard to the consumption of strawberries an increase of 14% since 2000 has been recorded. From 2000 to 2004, consumption increased from 61,000 tons to 73,000 tons with an increase of 21% and in 2005 there has been a contraction, plotting the values around 67,000 tons.
In many countries, the quality of the production of strawberries was considered as a secondary element at the expense of other characteristics, such as production capacity and appearance: however, changing need and necessities, especially related to consumer tastes and to the fruit and vegetable market the quality of strawberries now represents an element of great importance, more and more central in genetic improvement programs. Sweetness, acidity and flavour are, indeed, the major components of the taste of the fruit and their balance influences the appreciation of the consumer.
Like all varieties of fruit and vegetables that are more traded, even strawberries are now evaluated from an organic point of view, in accordance with the possible parasite control done through the available phytosanitary products; nowadays more attention is given to organic agriculture and with it to the production of organic strawberries, as it is a farming that aims at prevention and acts especially to improve soil fertility, with the purpose to control, reduce or eliminate cultivation problems.
Hydroponic cultivation of strawberries, has largely developed in recent years, especially along the Italian Adriatic coast and abroad for the industrial production in greenhouses.
Hydroculture in general, and that of strawberries in particular, allows to optimize all the elements responsible for the quality of the plant and of the final product, allowing also a higher production of strawberries of better quality, eliminating problems that arise from ground cultivations (dirty, slow, fungi, molds...) ad stardardizing the production of strawberries.
In many provinces of Italy, in recent years, has assumed increasing importance the production of organic strawberries.
The choice of the variety of organic strawberries represents a decision of great importance to the technical-economic success of cultivations, especially in low impact organic agriculture. The variety of organic strawberries to plant, must necessarily be more resistant than others, they have to be vigorous, hardy and constantly productive, producing big, bright fruits that keep their colour also after storage. These characteristics for the production of organic strawberries of course, should not exclude also a high quality standard, which is able to convey a commercial strength to the sale of organic strawberries.
The genetic improvement, public and private, has introduced, in recent years, a number of new genetic accessions, resulting in an adaptation of varietal availability.
Today, the varieties of organic strawberries that are more cultivated are:
Other varieties of strawberries suitable to organic farming and to the production of organic farming are: Strawberries "Alba", "Onda", "Clery", "Roxana", "Patty" and "Queen Elisa". The last two varieties, in particular, differ for their hardiness, in other words for their capacity to adapt to different pedoclimatic conditions. On the other hand, we recommend not to use in organic farming less hardy varieties, such as Miss and Marmolada, still used in the traditional farming.
- Asia strawberries: Early season variety, selected by da New Fruits, that follows as to ripening the variety Alba. Fruits are cone shaped and very attractive, they have a good size and good organoleptic qualities. The colour becomes dark in case of high temperatures. The fruits' testure is not very good, and the plant is sensitive to anthracnose and phytophthora.
- Antea* strawberries: variety selected by the Civ from Ferrara (Italy), it ripes little after the variety Alba and can be harvested for a very long period. It is a vigorous plant with a high level of productivity. Its inflorescensces are very long and it is important to remember it during transplantation, paying attention that there is an adequate distance between plants. Fruits are intensely coloured, cone shaped, quite tasty and with a consistency superior to average, with great advantages in the processing of the product after harvesting.
- Record strawberries: late season variety, selected by the section situated in Forlí (Italy) of the Cra-Istituto sperimentale per la frutticoltura (Fruit Research Unit), it will probably replace the "Idea" variety, compared to which this variety is better in fruit texture and colour that is more bright. The flesh is clear and tasty. The plant is vigorous, hardy, has a high level of productivity and fruits are of a good size throughout all the period of harvesting. Fruits concentrate around the collar, being this way protected from sunburn and from light hails. We suggest an early transplantation.
Hydroculture is a system of techniques that permit to cutivate fruit and vegetable products in greenhouses on an inert substrate or not, through an oprimal managing of the elements that determine the quality of plants and of the product: temperature, irrigation, light.
Hydroculture in general, and that of strawberries in particular, permits to optimize all the elements responsible for the quality of the plant and of the final product, guaranteeing a high production and a better quality, eliminating problems that come with the cultivation in ground (dirty, slowness, fungi, mould) and standardizing the production.
Furthermore, hydroponic cultivation of strawberries can be done also at home, for smaller cultivations, thanks to low prices and to the fact that installation is very easy.
In the world fruit and vegetable sector, the introduction of the soilless cultivation of strawberries was enhanced by specific structural and environmental condition of this cultivar: in recent years, in fact, the cultivation of strawberries has had a very fast evolution, changing from the classic cultivation in the ground to the soilless cultivation on a substrate and in particular on bags of peat.
With hydroponics strawberries are constantly kept in optimal nutritional conditions, as techniques used guarantee better phytosanitary conditions and a more clean product; as a result, we have strawberries superior in quality, with a better appearance, a uniform size, better intrinsic characteristics (less content of raw fiber, a higher percentage of sugars, fats and vitamins, a higher specific weight), a lower availability and finally a better resistance to long distance transport.
Strawberries cultivated with the hydroponic techniques are protected through different types of tunnels that, according to the costs of investment and amortization, bring air from the heads and from the sides or from the tops and the sides: they usually are single plastic films that last 3-4 years, with medium characteristics of light and a good warmth.
The bags for the cultivations can be laid against a series of pedestal rows or hanged at a hight at which the product can be easily reached by farmers.
Plants of strawberries are planted out in plastic bags (4-6 per bag) of 10-12 liters each, with size ranging from 20-25 cm in width and 35-40 cm in length.
These bags usually contain white peat and perlite in variable percentages.
Recently in Netherlands has spread also the habit to use bags with mineral wool, which seems to give good results as to production and to ease any changes in fertilization and irrigation needed by hydroponic cultivations of strawberries.
However, there are many type of hydroponic cultivations for the production of strawberries, which differ for the way in which water reaches the roots of the plant.
In general we distinguish:
In hydroponic cultivation, all the varieties mentioned in the section "The varieties of strawberries" can be used, however the most common are:
- Hydroponic cultivation of strawberries with substrate.
- Hydroponic cultivation of strawberries without substrate.
- Hydroponic cultivation of strawberries with drip system irrigation.
- Hydroponic cultivation of strawberries with seepage irrigation.
- Hydroponic cultivation of strawberries with an open system.
- Hydroponic cultivation of strawberries with a closed system.
- "Ostara" (Figure 2): everbearing variety, harvested starting from June, with typical big, cone shaped fruits and a juicy and firm flesh. It is usually sold in pots. Strawberries 'Ostara' (Fragaria x ananassa) is a perpetual strawberry that produces flowers and fruits all summer long, from June until the frost. 'Ostara' is one of the tastiest varieties. The cone-shaped, deep red fruit are aromatic and full of flavour. The plants are prolific giving fruit in summer and autumn. They are beautiful to behold and amazing to eat! Plant your strawberries in layers or in containers to create a spectacular feature. Fragaria x ananassa 'Ostara' are happy in most types of soil, so they can be grown just about anywhere. Strawberry plants adapt readily to most conditions and give results anywhere. They do like sunshine and strawberries grown in a sunny position will be sweeter. You can plant strawberries straight into the ground or in pots or planters. Don't forget to water them from time to time. Improve poor garden soil by mixing in some compost and Bakker's strawberry fertiliser. Make mounds of about 35-40 cm high around the strawberry plants and cover them with foil. The distance between rows should be 80 cm. Make crosses in the foil using a sharp knife and place the plants inside. The planting distance is 30 cm. Water immediately after planting. The soil should not be dry during the winter but neither should it be too wet.
- "Mara de bois" (Figure 3): everbearing variety, harvested from June to December, with a flavour that reminds that of woodland strawberries. it is a very productive variety, with about 900 gr of strawberries produced per stem. This variety of cone shaped strawberries, is recommended especially for desert recipes. 'Mara des Bois' was hybridized in Soings En Sologne France in 1991 by strawberry breeder Jacques Marionnet in a planned breeding program involving a cross of (Fragaria "Gento" x Fragaria "Osara") x (Fragaria "Red Gauntlet" x Fragaria "Korona"). It is a remontant (everbearing) variety that produces fruit in summer to early fall in the first year, but in subsequent years produces a heavy spring crop with continued production throughout the growing season. Plants typically grow to 12-15" tall and spread to 12-24" wide. Conical red berries are plump, fragrant, sweet and exceedingly tasty. Five-petaled white flowers with yellow centers appear throughout the growing season on stems clad with tri-foliate green leaves. Flowers are followed by edible, bright red strawberries (to 2.5-2.6 cm long) that may be harvested throughout summer. Berries are small to medium (acorn size), which puts them in the category of being much smaller than most commercially grown berries but larger and firmer than tiny wild strawberries. U. S. Plant Patent PP8,517 was issued on December 28, 1993. This patent expires in September of 2011. May be grown in beds or containers (strawberry jars). By reputation, "Mara des Bois" has the best flavour and fragrance of any strawberry currently in cultivation. Unfortunately, picked berries have a shelf life of only 5 days which is fine for home production or for local sales, but way too short a time for commercial production and shipment.
- "Maestro" (Figure 4): everbearing variety of strawberries, whose fruits are juicy, with a firm flesh and very tasty. This hydroponic variety of strawberries was once better known with the name "Mareva", but it was later modified in "Maestro". This variety replaces the "Gento" for its fast and strong rooting, the hardy vegetation and the level of production, that can reach up to 1 kg of fruits produced per plant. The characteristics of "Maestro" are:
The Strawberry plant is a perennial appreciated for its abundant production of small fruits. It is also used as a ground covering plant, or to ornate the soil of a border in an original way.
- Adult dimensions: height up to 30 cm, width up to 30 cm.
- Foliage: evergreen, Perennial.
- Type of soil: rich in humus, clayey, acid to neutral.
- Hardiness: hardy to -20 °C.
- Site: full sun.
- Plantation density: 2 to 3 per m2.
The strawberries are gathered when they are bright red and come away easily. Fragile, they do not keep very long. Rich in vitamins and with low calorie content, they are the summer fruit 'par excellence'. Eaten raw, in jams, in fruit purées, in tarts, they will delight the young and the adults alike.
Before the winter frost, cut your strawberry plants to a 5 cm height to allow them to go happily through winter.
The strawberry plant "Maestro" is a late double-cropping variety, which is best associated with an early, single-cropping strawberry plant to vary the flavours. This strawberry plant has a good yield and produces large, tasty fruits.
- "Gariguette" (Figure 4): early season variety of strawberries, harvested from the 15th May to the 15th June, with long, bright red and flavoured fruits.
Figure 2 - "Ostara", a variety having an incomparable flavour, is very productive and very resistant to diseases.
Figure 3 - "Mara de bois" is not a wild strawberry or an antique variety. It's a fairly new hybrid of the "regular" garden strawberry, Fragaria ananassa, developed for its intense flavour by strawberry breeder Jacques Marionnet, in a planned breeding program involving a cross of (Fragaria "Gento" x Fragaria "Osara") x (Fragaria "Red Gauntlet" x Fragaria "Korona"), and introduced as a patented variety in France in 1991. The berries don't travel as well as grocery store varieties, but they have great gourmet appeal to local growers and home gardeners. Best grown in humusy, fertile, medium moisture, well-drained soils in full sun to part shade. Prefers full sun. Plants spread indefinitely by runners that root as they go. Plants generally dislike high summer heat, humidity and strong drying winds. Therefore, strawberries are susceptible to a number of fungal diseases including anthracnose, leaf spots, rots, wilts, powdery mildew and blights. Insect visitors include spider mites and aphids. Leaf scorch may occur in hot summer climates.
Figure 4 - "Maestro" is a late double-cropping variety, which is best associated with an early, single-cropping strawberry plant to vary the flavours.
Figure 5 - "Gariguette" a variety that dates back to the 1930s and is considered to be the French equivalent to "Royal Sovereign" on account of its pleasing fragrance and sugar-sweet flavour. The elongated fruits are a brilliant vermilion-red. The flesh is delicate, soft and particularly juicy and totally mouthwatering, add sugar and cream and it is at its most delectable. "Gariguette" is grown commercially in Provence and brightens up the local market stalls during the early summer. The flavour is excellent.
Other interesting varieties of strawberry are represented in Figure 6 and Figure 7.
Figure 6 - Some interesting varieties of strawberries are shown: "Flamenco", "Florence", "Malling Centenary", "Malling Opal", Cambridge Favourite", Elegance", "Malwina", "Royal Sovereign", Snow White", Tallara", "Sweetheart", Vibrant", Red and White, Planter together with strawberry plants, "Joly".
- "Flamenco" is ever bearing selection combines exceptional fruit quality with good yield potential. Medium to large fruit with a glossy orange colour with an excellent flavour. Peak production is in early September.
- "Florence" is a Fragaria x ananassa, hardy perennial, for late season, bred by HRI East Malling, this is an excellent variety for firm, flavoursome, well coloured fruits. Strawberry "Florence" is ideal for a late season harvest producing delicious sweet strawberries from the end of June to the end of July. A prolific cropper with exceptional pest and disease resistance. Strawberry "Florence" is well suited to growing in containers for a space saving crop on the patio. Cropping periods can also be brought forward or extended if you are growing them in a greenhouse or polytunnel. Height: 20 cm (8). Spread: 30 cm (12); estimated time to cropping once planted: 4-8 months; estimated time to best yields: 16-20 months.
- "Malling Centenary" was released in 2012 by East Malling Research and the Strawberry Breeding Club. "Malling Centenary" has the potential to be of real value to intensive growers seeking to grow a better eating variety for their supermarket customers. This main season selection has been released as a direct result of its significantly improved flavour, appearance and shelf life compared to Elsanta. The fruit is very regular in shape, firm in texture, attractive in appearance and with excellent flavour. The 2012 HDC substrate trial, using tray plants planted into coir at the end of June, Malling Centenary, produced 440 grams per plant of Class 1 fruit in the first season, 22% more than Elsanta and 717 grams of Class 1 fruit in the following summer, 73% more than Elsanta. The Class 1 percentage was very high and comparable with that of "Vibrant", and over 50% of the berries were 35mm or larger. The season is a few days ahead of that of "Elsanta". Malling Centenary does not have strong resistance to disease and ill need to be grown with care. Meiosis Ltd will extensively sample this variety to the major multiples during the 2013 season.
- "Malling Opal" produces large, attractive, conical berries with a particularly good sweet flavour and juicy texture. This variety is larger fruited and higher yielding than its sister seeding, Malling Pearl, with better presentation of fruit but shelf life and fruit firmness are slightly weaker. "Malling Opal" is a vigorous early season everbearer cropping heavily in July and August. Less susceptible than "Malling Pearl" to Crown Rot and with moderate resistance to Powdery Mildew and Verticillium Wilt.
- "Cambridge Favourite" has an enduring popularity that has made it one of the most well-known and best-loved varieties available. This mid-season strawberry produces a bumper crop of juicy orange-red fruits with an excellent flavour and texture from June to July. This superb variety is reliable and tolerant of most situations. Strawberry "Cambridge Favourite" is well suited to growing in containers for a space saving crop on the patio. Cropping periods can also be brought forward or extended if you are growing them in a greenhouse or polytunnel. Height: 20 cm (8). Spread: 30 cm (12). Estimated time to cropping once planted: 4-8 months; estimated time to best yields: 16-20 months.
- "Elegance" is a serious contender to replace the industry standard of Elsanta, currently accepted by most major multiples. This particular berry is an excellent all-rounder with two exceptional qualities. Firstly, the look is perfect as the name suggests and secondly, the yield is as much as 175 g/plant more than "Elsanta". Good news here, Elegance will grow anywhere as long as the roots are in the soil or sub straight. Elegance will yield well in any system, though it lends itself particularly well to open field growing. The plant is vigorous and has a good tolerance to major diseases and very good rain tolerance.
- "Malwina" is the latest ripening among the currently available strawberry varieties worth growing. It is going to set new standards for late season varieties in the direct marketing segment. Already under standard cultivating conditions, the peak season is some 22 days after "Elsanta" (12 days after Florence). When straw covering is applied it ripens as late as about 30 days after "Elsanta". "Malwina" is a crossbred of "Sophie" x a clone from Schimmelpfeng, Weihenstefan. The crossbreeding was done in 1998 by Peter Stoppel, Kressbronn. The plant is very robust and vigorous, with dark green, medium sized, glossy leaves. "Malwina" blooms under the foliage and is self-pollinating. The berries are large, firm and feature a glossy mid red. When picked pale red (wholesale marketing), their flavour is good and excellent when picked fully ripe. "Malwina" is a pleasure to the eye, in the basket as well as in the punnet. Its aroma reminds us of strawberries from grandmas garden, as a customer put it. Yields for "Malwina" are about 1015% lower than that of Elsanta (and about 20% lower when straw covering is applied). The percentage of large fruits is 85% (about 77% with straw covering). That means the proportion of marketable Class 1 fruits is higher than with Elsanta. The picking rate is between 10 and 15% lower, though, due to the short pedicels and the ample foliage. About 3% of the fruits feature so called leaved inflorescences. The genetic defect behind causes small leaves emerging from the fruits on about one fruit per plant. Malwina is very hardy and resistant to diseases. For example, it is tolerant to Verticillium, very little susceptible to fruit rot. Malwina withstands intense rain and is little susceptible to sunburn.
- "Royal Sovereign" tried and tested strawberry still remains very popular due to its superb flavour. Strawberry "Royal Sovereign" crops from July, producing large, wedge-shaped, bright scarlet berries. Our quality strawberry plants are produced from certified mother plants that are inspected and renewed annually. Prior to packing, the plants are checked and graded by hand ensuring that you receive the best quality plants guaranteed to produce the highest yields of flavoursome fruit. Plant 40-45 cm (15-18 in) apart.
- "Snow White" has an unique and highly unusual fruit is like a strawberry in reverse, with snow white flesh (hence the name) and bright red pips. It has a mouthwatering flavour, similar to pineapple, and an intense fragrance which makes it perfect to eat fresh or even as part of a wonderful dessert. Planting in Autumn is ideal as the soil is still warm and will allow the plants to establish nicely and will help to give you bumper crops next year. Strawberry 'Snow White' is winter hardy and easy to grow. Bareroot plants supplied.
- "Tallara" resulted from a cross between "Parker" and "Pajaro" made in 1988 at the Institute for Horticultural Development, Knoxfield, Victoria, Australia, and tested under the selection number 88-022-296. Berries of Tallara are large and highly attractive, being orange red in colour and very glossy. Shape is uniformly conical with little variation between primary and secondary fruits. Flesh is medium red with a lighter coloured core, substantially firmer than Pajaro and moderately resistant to rain damage. The calyx detaches easily and is slightly reflexed. Plants are vigorous with medium green leaves and an upright growth habit.
- "Sweetheart" is a modern variety bred at the famous East Malling Research in Kent, and has proved to be one of the best varieties to offer in this way. Its sweet and juicy berries are conical in shape and have good colour and the taste is just delicious with good old fashioned flavour. The plants have a good habit and the fruit is well displayed too. This unique method of production begins in September and October when plants are lifted from the field with the flower initiation process already started they are then frozen. The next process happens around the middle of April when the plants are thawed, potted and grown on for 30 days at our nursery. By the middle of May the plants are well developed and have just 30 days of growth remaining, to the first sweet and juicy berries being ready for picking.
- "Vibrant" is a bred and selected by East Malling Research, Vibrant is a high yielding, high quality early variety that has rapidly become established as the premier early selection and has advanced the English strawberry season by ten days. "Vibrant" produces beautifully shaped, uniform, conic berries which are medium to large in size and with virtually no Class II fruit. The berries are glossy, brilliant red in colour and are carried on strongly erect, long, flowering peduncles. Vibrant was bred to give a high 60-day yield by producing a large number of flowering trusses in succession thus cropping over an extended period. Each truss carries only 4 to 5 flowers thus maintaining a larger fruit size (72% of the Vibrant crop exceeded 35mm compared to 56% for Elsanta in the Hoogstraten trial). Maincrop yields have been consistently good and have normally exceeded 1kg per plant. Picking speeds are exceptional due to the good presentation of the berries and the fruit is easily handled and packed being firmer than both "Clery" and "Elsanta". Flavour is excellent and Vibrant was the top rated selection for flavour in the HDC Substrate Trial in 2011. A genuinely early variety with a 50% pick date at least seven days ahead of "Elsanta". Picking commenced in Suffolk under plastic on 22nd< April in 2011 and in Kent on the 15th April 2012. The plants are moderately vigorous with good resistance to Powdery Mildew and Crown Rot but are susceptible to Verticillium Wilt. A second crop can occur if the crop has been forced and up to 400 g of good quality fruit can be produced from July onwards.
- "Red and White" is an exceptional mixture of colour, amazingly sweet alpine strawberries. Generally fruiting in the first year, they are a must have for patio containers. With generous crops and the added benefit of birds not recognising the ripe white strawberries
- Planter together with strawberry plants.
- "Joly" have high chill June bearer, good vigor, high productivity; it is of mid season; high quality fruit; regular conical shape, bright color, high % class 1 grade, firm, very good taste, easy fast picking, high production with misted tips in tunnels, very good results in 60 day cropping systems.
Figure 7 - Some interesting varieties of strawberries are shown: "Dely", Clery", "Nabila", "Rania", "Linosa", and a technique of soilless cultivation of the variety "Clery".
- "Dely": plant with high chill requirement. The plant has medium-high vigor, and an average foliage density. Rustic plant, quite resistant to lead and root diseases. Very high productivity. Harvest is long lasting and usually has a second flowering. Flowers: within the foliage, medium size, rich in pollen and very easy pollination. Blossoming time: early and continuous throughout the season. Harvest: early, harvest season begins at about the same time as Clery but lasts longer. Fruit: short heart-shaped, with medium sized calyx, large berries. Fruit color uniformly bright red; red flesh, good texture and firmness. The flavor is excellent, very fragrant with hints of wild strawberry. One of the best varieties for those who love aromatic strawberries. Its exceptional organoleptic characteristics make this fruit ideal for P.Y.O., direct sales and fine pastries.
- "Clery": trademark registered by CIV (Consorzio Italiano Vivaisti).Plant: clery has a medium-strong vigor with medium density. The variety is very rustic and is tolerant to diseases that affect the foliage and root system. Medium-high productivity of cold-stored plants and very productive misted tip plants, minitrays and trays. The plant is also well suited to difficult soils, ideal for early production in tunnels or glasshouses. Flowers are rich in pollen with good resistance to frost. Harvesting season: very early and concentrated, one to two weeks ahead of Elsanta depending on cropping system. Fruit: regular fruit size, conical shape, bright red, , very firm, sweet with good flavour.
- "Nabila": plant with low chill requirement, suitable for Mediterranean climates. Variety is of medium-high vigor, with medium dense foliage, semi-upright habit. Rustic plant, quite resistant to leaf and root diseases. With robust and efficient root system, the plant adapts well to tired soils, generally does not require soil disinfection. Due to its hardiness and vigor, it is well-suited to replanting method and requires a moderate amount of fertilizers. Productivity is very high, greater than that of standard varieties. Harvest is continuous with a long duration. It is well suited to be used both as a fresh plant as a frigo-plant; the latter gives a good crop for autumn harvest. Flowers: large flowers, very rich in pollen; pollination is quick and efficient, even under adverse conditions such as low temperature, humidity, and light intensity. The flowers are slightly above the foliage, for the most part sustained by individual stems. Blossoming time: very early and long lasting. Harvest: it start very earlywith a large crop, then bear continues to fruit regularly over a long period. Fruit: regular conical shape with a medium sized calyx; the fruit size is consistently large. The color of the fruit is shiny red, very attractive, without darkening, even when fully ripen. Uniformly red flesh, of good firmness, resistant to handling. The flavor is very pleasant with highly sweetness. Fruit size and plant structure make harvesting very easy, which significantly reduces picking.
- "Rania": low chill requirement, suitable for Mediterranean climates. High vigor with medium dense foliage, and an upright habit. Rustic plant, quite resistant to leaf and root diseases. Robust and efficient root system, the plant adapts well to depleted soils, generally does not require soil disinfection. Due to its hardiness and vigor, it is well suited to tired soil and only need a small amount of fertilizers. High-yielding, 30-40% greater than of standard varieties. The picking season is long and constant. Flowers: large, very rich in pollen; pollination is quick and efficient, even under adverse conditions such as low temperature, high humidity and low light intensity. The flowers are slightly the foliage, supported on strong stems that bear a maximum of five flowers per stem. Blossoming season: early and long lasting. Harvest: it starts early and continues regularly for long time, delivering high quality berries of optimal size until late in the season. Fruit: conical-rhomboid shape with a medium-size calyx. The fruit size is consistently very large. The color of the fruit is bright red, without darkening, even when fully ripe. Uniformly red flesh, good firmness, very resistant to handling. The flavor is excellent, very sweet with a very good aroma. The fruit size and plant structure make harvesting very easy, which reduces picking costs significantly.
- "Linosa": everbearer, average vigor, high productivity. Blossoming time: Very early peak (needs attention for enough pollinators!) followed by a late peak. Harvest: very early and high yielding peak followed by a second peak from mid summer to the end of the season. The early peak in June shows excellent brix levels. Fruits: Conical shaped berries, very regular and attractive, large and uniform, extremely resistant skin. Orange red color with uniformly red and very firm flesh. Good and sweet flavor. The firmness of the fruit and the good color stability often enable a weekly harvest. The plant structure makes harvest easy. Very good shelf life.
- A technique of soilless cultivation of the variety "Clery".
Figure 8 - Shows the following varieties of strawberry: Miss, "Sugar Lia, "Ventana", "Alba", "Garda", "Anita", "Siba", "Irma", "Queen Elisa", "Roxana", "Maya", "Diamante.
The following varieties are represented in Figure 8 and are briefly described:
"Miss" is one of the most precocious cultivar. Precocity combines large size and beauty of the fruit, enhanced features in more protected cultivation in open field. The fruit is sweet, bright red and attractive, even after storage. To improve the low tillering of plants it is advisable to anticipate the plantation, especially in less fertile soils in late July. The harvesting is very easy for the ease of fruit detachment. The plant is susceptible to alternariose and Phytophthora cactorum.
Other varieties, some of which are of local interest are reported and shown in Figure 9.
- "Sugar Lia" among the qualities one must observe the early ripening, regularity of form, and finally, ease of separation and high sweetness and aroma of the fruit. Among the defects must cite the susceptibility of the plant to pathogens of the root system, which requires fumigated soils, which requires cold temperatures in winter.
- "Ventana" among the qualities high productivity, significant early ripening, large pieces of frutt, beautiful conical shape of the fruit and regularity of the same, intense colour and very bright, even in the winter months with low light. Among the defects are reminiscent of the susceptibility of the plant pathogen and salinity of soils and nutrient solutions that often result in the collapse of the plant in the middle part of the harvesting. In conjunction with temperature rise often has a color too intense and a loss of consistency; fruits are not very tasty.
- "Alba" a medium vigorous plant that can reach very high production, up to 1.2 kg per plant. It prefers continental climates and requires a high demand hours in the cold. "Alba" is shown for both the protected cultivation for the open field and is the reference varieties for organic production. It is widespread and popular in many European countries. The bloom is medium-early (+2 days than "Clery"). The age of onset is very early collection, contemporary "Clery". Being an early cultivar, the fruit is very large (25 g in weight), has a constant size from the beginning to the end of the collection is consistent, conical-elongated and regular. The epidermis, bright red and bright red flesh, has a good shelf-life. Discrete organoleptic characteristics of ripe fruit. The fruit, easy detachment allows collection yields 30% higher than any other variety. To produce high yields, we recommend an early transplant. "Alba" prefers well-drained soils, but little sandy and baulature high. "Alba" is sensitive to a variety Colletotrichum acutatum (anthracnose) and the Gnomonia fragariae (Leaf blotch and Stem-End Rot).
- "Garda": new strawberry varieties formed by the experimental for fruit, U.O. of Forlì, reconciles appreciated, such as high consistency pulp, good sugar content, excellent color and a perfect fit even in small sizes. In addition, the ease of separation of the fruit from the plant provides an important advantage, since it allows to reduce collection costs. "Garda" well is in the interest of the farmers due to the ability of the plant to produce both in spring and in autumn. "Garda" is, therefore, a weapon for the conquest of the European markets, especially Germany, which accounts for a good chunk of red horticulture. It should not be overlooked that Verona cultivates 500 hectares of strawberry, mostly concentrated in the lowlands to small businesses. The Veneto controls 20% of the national strawberries. According to Istat data, Verona in 2011 produced 119,470 quintals of strawberries has about 60,009 under greenhouse and 4,410 q of 42 ha in the open air.
- "Anita" variety of Italian origin that has positive features of good productivity, good flesh firmness and refractometric degree high. Unfortunately, presents a very delicate surface of the fruit which leads to a considerable difficulty in the stages of collection, transportation and storage.
- "Siba" variety of high productivity, high sugar and high consistency.
- "Irma" was obtained by the working group set up by the Institute for Fruit Growing experimental, Section of Forlì, Experimental Institute of Fruit Growing in the province of Verona and ApoScaligera within the Project Mipaf "Fruit", with the financial support of the Province of Verona and ApoScaligera. The cross was made in 1995 between the varieties flourishing length neutral "Don" and a selection unifera deriving from "Addie" and "Earliglow" (grandparents) and "Marmolada" (a parent). You have selected to Verona in 1997 by W. Faedi, G. Baroni, L. Ballini, G. and F. Baruzzi Zenti. "Irma" is a re-flowering variety with good length neutral capacity to flourish, suitable for autumn crop in Verona where it is able to produce from October until December. The productivity of the plant did not differ from "Patty", both in the autumn and in the following spring. Even the fruit size did not differ from that of "Patty", while the result is definitely easier detachment of the fruit, which allows a significant increase of the yields of collection. Econsistenza sweetness of the pulp were higher in autumn than in spring, but in any case you are differentiated from "Patty." "Irma" is able to extend the timetable for the production of strawberries in the summer taking advantage of the ability to flourish. It appeared interesting for the distribution areas of the Cuneo area cultivated with the traditional technique adopted for the re-flowering variety, which involves the planting of plants cold stored at the beginning of April and the collection since the beginning of July to mid-October. Of particular interest is the high productivity of the plant combined with good fruit size. For traditional crops Romagna, both in tunnel and in open field, you can take periods of planting more later (early August) compared to those of other cultivars floricanes.
- "Queen Elisa" was obtained by the working group set up by the Institute for Fruit Growing experimental, Section of Forlì, and by the Research Centre of crop production in Cesena, as part of the Projects "Fruit", mainly funded by Mipaf, and strawberry cultivation environmentally friendly, funded by the Region of Emilia-Romagna. Derived from a cross made during 1994 between the Italian variety "Miss" and the American selection USB 35 ("Lateglow" × "Seneca"). You have selected to Cesena, in 1996, by Walter Faedi et al. "Queen Elisa" has distinguished itself from all other varieties that currently make up the standard varietal Cesenate for its excellent fruit quality, for the remarkable consistency, coupled with high aroma and sweetness due to the high sucrose content.
- "Roxana" Selected in the experimental fields of the New Fruits sas and widespread in 2001, presents an era of medium-late flowering and harvesting time mid-late (8 days. 5 days after Miss and. later Maya). The plant is of medium vigor with a spreading habit and high productivity. The leaves are medium in size and dark green. The flowers are of good size and remain below the level of the foliage. The fruit is very large, with conical-oblong, smooth and dark red brilliant. The achenes are at the same level of the epidermis. The cup is slightly detached from the fruit. The collection is facilitated by the easy detachment of the fruit, who also have good resistance to transport and handling. It 'a cultivar suitable for the North Central environments. It has a good tolerance to the most common fungal diseases such as powdery mildew, Alternaria and pitting. Gives good results in tunnel grown both in open field and using both cold stored plants that fresh plants (rooted peaks). Moreover, it can present a good adaptability to both the cultivation of spring, which in the autumn (giving otiime productions both in quantity and quality 'of the fruit), and both in soilless cultivation. The time of planting is recommended that medium-early. It may be considered the most cultivated in Verona.
- "Maya"is a medium-early variety (+ 4 "Alba"), a plant vigorous and rustic, it fits very well in less fertile soils; is tolerant to the most common bacterial and fungal diseases. The fruit is medium-large (weighing on average 24 g), a reddish orange color. It is recommended that the cultivation in the tunnel.
- "Diamante" is re-flowering varieties suited to large areas of cultivation and of great interest to those in the northern mountains where it provides fruit of high solids and good quality throughout the summer-autumn period. The ability to flourish is not high and inconstant in the summer period. The plant is very susceptible to anthracnose, great is the shelf life of the fruits.
Figure 9 - Shows the following varieties of strawberries, some of which are of local interest: "Tudla Milsei", "Naiad", "Candonga Sabrosa", "Carmela", "Pircinque" e "Sabrina".
The following varieties, which are shown in Figure 9, are briefly described:
The following are other varieties which were the starting material for the creation of new varieties of strawberry and strawberry cultivation has been an interest in the local and national level:
- "Tudla Milsei" is a unifera variety of Spanish origin with medium vigor, with great hardiness and early maturity; the
fruit has some problems with pollination in early flowering, with consequent high reject rates for deformed fruits, and shows
sealing problems at high temperatures and the staining of the apical part. The production unit is instead very good, as well as the uniformity of production
(size fairly constant) during the harvesting season and the elongated shape of the
fruit. Suitable for growing under glass-single tunnel and tunnel but also to
tunnellino and especially to ski material "fresh". It is susceptible to Oidium and
to the attacks of Frankliniella occidentalis. In recent years it has been gradually replaced by
various quality parameters that ensure higher and more consistent, and eventually disappear
- "Naiad" unifera selected varieties in Italy, affecting productivity and the quality of the
fruit (hardness, resistance to aging, sugar level, brightness), although
in the advanced stage of the harvest season tends to be too dark hue;
shows some limits from the point of view of the size of the fruit at harvest
advanced and, depending on the season, the precocity. the plant
cold storage is well suited for growing under little tunnel, while in protected culture
the plant behaves very well in the "top-rooted," capable of
ensure precocity, with production levels and satisfactory quality. From the point of view the plant were found to be sensitive to Oidium.
- "Candonga Sabrosa" is a Variety unifera Spanish, widespread in different sites of the strawberry cultivations of the southern, where it is
established for the very valid qualitative characteristics. In local conditions has
confirmed the high level of quality, showing good general rusticity
although on average the production and precocity not seem to meet
completely local producers. The type of plant is the most widespread fresh root "naked" in order to ensure good
production levels, however, must be handled with great care in the autumn -
winter, ensuring consistently high nutritional benefits. These are the characteristics
qualitative (general appearance of the fruit, conical shape - elongated very smooth, hardness, gloss, resistance to over-ripening, flavor balance) that
make it interesting that variety. In addition to the data on the precocity and production level in
absolute value, some concerns were raised over the last few years
characteristics related to the average weight and, from the point of view of plant health, a certain
sensitivity to Oidium.
- "Carmela" is a variety unifera selected in Spain, which was introduced in some areas of Sardinia, has provided some good impressions, especially for what concerns the data on
productive capacity and precocity, certainly higher than Candonga. Shows, also, a certain regularity in the fruit size and a low
percentage of waste in the first collected, and a definitely higher degree Brix
to Tudla. Finally, quite satisfactory grip characteristics to
overripen and color. These assessments have determined that it is imposed in the territory as a true
alternative Tudla, being able to provide a compromise between production capacity
(exceeding Candonga) and satisfactory quality parameters.
- "Pircinque" was selected as part of the Project MiPAAF "Breeding"
- "Sabrina" is a variety of the Spanish Constitution introduced in areal Italian.
- "Marmolada" variety very productive especially in protected cultivation. The result of high solids, consistent, good-looking and taste characteristics medium-low. The plant is rather small, it is recommended especially in protected cultivation where the fruits are less susceptible to rot. The advance of ripening due to the protection avoids the darkening of the color of the fruits, which occurs in the warmer periods. The collection of fruits is not very easy because of the separation difficult. It is advisable to delay planting in the first decade of August in order to achieve a better balance between vegetation and production of plants. This variety has high productivity, resistance to cold (it is preferred to "Elsanta" in the higher elevations, from 1300 to 1700 m). The defect is a high susceptibility to pathogens of the root and powdery mildew.
- "Don" is the only flourishing length neutral cultivars (character "DN", but with low capacity to flourish). It is characterized by high productivity and constant, equal or superior to the best cultivars floricanes. It has elongated fruit, medium sized, valued at the commercial level, more enhanced features in protected cultivation in open field, where the fruits take quite intense colors. The time of planting is similar to that recommended for Marmolada. The plant has shown a remarkable susceptibility to alternariosi and low susceptibility to powdery mildew.
- "Onda" is a viable alternative to "Marmolada", from which it derives. The plant is very productive, vigorous tillering limited. The flowering time is late, and the harvest period is similar to the intermediate "Marmolada". The fruits have a regular conical shape and large size uniform until the end of the harvesting. The surface is durable, dry, deep red and bright even in the presence of temperature rise that often occur during harvesting in the open field. This aspect combined with the high consistency makes the fruits of "Onda" of great commercial interest. The plant is also suitable for non-fumigated soil, showing a remarkable tolerance to the main radical apparatus diseases (Rhizoctonia spp., Phytophthora cactorum and Verticillium spp.) and Alternaria alternata and Colletotrichum acutatum (anthracnose), but is susceptible to Xanthomonas fragariae . It is advisable not to delay planting beyond July 25.
- "Patty" has the plant that is very vigorous, tillering medium-high and high productivity. The result of conical-rounded, large size, which tends to decrease at the end of the collection, consisting of medium good taste characteristics. It provided a good productive behavior in most of the northern cultural environments, even if proved to be more interesting in the autumn crops Verona for quality productions autumn and spring. It has an interesting behavior even in protected crops Cesena. In the less fertile soils or non-fumigated the force is smaller and the plant has good production levels, greater early ripening and limited susceptibility to rot. The behavior in organic farming has been very positive, easy detachment from the fruits of the cup allows rapid collection (for "milking") of organic fruit stalk is removed in high demand from the market for industrial uses. It has provided good results even with fresh plants' tops rooted "planted in the first week of August. The less positive aspects of this variety are: the difficulty of separation of the fruits in the early stages of the collection; the need to make collections approximated in order to avoid excessive darkening of the color of the fruits; the limited consistency of the fruit; the susceptibility of the leaves in Xanthomonas fragariae.
A correct technique of strawberry nutrition is essential not only to maintain an adequate level of soil fertility, but also to avoid the plant nutritional imbalances and to reduce the environmental impact that this practice, if poorly managed, can be determined.
In order to determine the amount of fertilizer to be administered is essential to the understanding of the characteristics and nutritional status of the soil through its analysis.
The analytical values obtained are then compared with those of "reference", variables in function of the type of soil.
To set a plan for rational fertilization, it would be useful to be able to refer a soil analysis that determines the pH at least, the provision of macro and salinity. Given the general poverty of the organic matter of the soil on which it is normally cultivated strawberry, you should deploy on the previous crop or a few months before the transplant, manure mature (at least 400 kg/ha) or, failing that, 12-15 q (localized on the row) of commercial organic fertilizer. The contribution of organic acquires greater importance when using the plants growing outside ("fresh plant").
Nutritional requirements of the strawberry crop: knowledge of the amount of nutrients absorbed by the strawberry plant to complete its growing cycle and production, it is essential for the rational management of fertilization. In addition the total removal is important to consider the dynamics of the absorption of the main elements and the proportional distribution between the different phenological stages of the crop.
It should be also considered that the crop residues are usually removed completely from the field to the end of the harvesting season, for which the data on the removal can be assessed as the total net removal refers to the dynamics of the absorption and therefore the removals can be influenced by the nature of the terrain, the weather conditions, variety and cultivation technique employed.
Are shown in Table 2, the average data of removal of the three fundamental nutritive elements (nitrogen, phosphorus and potassium) for a unitary production of strawberry.
| Table 2 Average data of removal of the three fundamental nutritive elements (nitrogen, phosphorus and potassium), in kilograms, to a unitary production of strawberry (1 ton of product).
The aggregate quantity of different nutrients to be distributed on crop fertilization plans should be calculated by taking into account a number of parameters such as physic-chemical characteristics of the soil, removal of the crop, irrigation system, varieties, preceding crops, cultivation technique, contributions of organic substance.
The Regional Integrated Production Regulations provide for the calculation of a fertilization plan analytical or, alternatively, the use of a simplified model that refers to the cards to standard dose. The standard dose should be understood as the maximum amount of each macro to be taken as reference in conditions considered ordinary yield, fertility of soil and climatic conditions. Standard doses may be increased or decreased on the basis of a series of situations indicated specifically in the tabs of fertilization.
Are reported in Table 3, the maximum total inputs of nitrogen, phosphorus and potassium provided for strawberry and calculated through the forms to standard dose, for strawberry yields between 240 and 360 q/ha.
| Table 3 Maximum total inputs of nitrogen, phosphorus and potassium for strawberry provided through the forms of the standard dose, for strawberry yields of between 240 and 360 q/ha.
It occurs at the highest dose, which can be reduced or increased (up to a maximum of 40 kg) upon certain situations indicated in the standard dose forms.
The variability is related to the provisioning of the soil. The standard dose forms provides the ability to reduce or increase the indicated dose.
Depending on the equipment of the soil. The standard dose forms provides the ability to reduce or increase the indicated dose.
Of course, the total doses of fertilizer, specifically calculated, will naturally divided between inputs in pre-transplant and distributions during the production cycle.
Fertilization basic (in pre-transplant) should be distributed during the preparation of the soil before laying the mulch. In very sandy soils in texture, it is necessary to minimize the nitrogen intake in pre-transplant, with compensating actions nitrogen in coverage. If the same soils have a pH value of sub-acid and are generally well equipped with phosphorus and poor of cationic elements (calcium and magnesium), requires action in consequence decreasing the integration of phosphate fertilizer and increasing the calcium and magnesium. It should also be pointed out that we must well consider the type of phosphorus in the soil; if phosphorus soil is all just exchangeable, such as Ca3(PO4)2 (tricalcium phosphate), the soil should be considered as poor in phosphorus and intervene with phosphate fertilizer.
In this regard, refer carefully to Table 4 and Table 5.
| Table 4 Units of nutrients normally used for basic fertilization in pre-transplant of strawberry cultivation in sandy soil.
If you use slow-release fertilizer, the amount of nitrogen fertilizer administered to the soil with the basic fertilization can be increased.
In soils with pH values higher and better with regard to the assimilable calcium you will naturally limit or avoid the supply of agricultural lime.
| Table 5 Total units traditionally considered in the conditions of production about to sandy soils.
Ternary fertilizers 12-12-17
Potassium sulfate magnesium
In soils with more clayey texture you can increase the amount of nitrogen fertilizer to be distributed with the basic fertilization. Also for the other elements will always be important to calculate the inputs and the distribution according to the physical-chemical properties of the soil.
Fertilization after transplant
It is carried out exclusively through different types of installations for fertigation, with the aid of the self-compensating hose or wing dripping.
In the immediate post-transplant may be used for stimulating plant that favor the formation of a good root system and, if necessary, the starter nitrogen (calcium nitrate) or water-soluble fertilizers as balanced (20-20-20) for promote good training for the growing season. Fertigation management differs greatly depending on the planting material used for transplantation.
Field with material cold-storage
During the differentiation of floral and vegetative rest of the plant (December-January), will not be given nitrogen fertilizer. In the immediate vicinity of the bloom can be made fertilizer with a high phosphorus content, and only after fruit set can resume regular fertigation, with a ratio N / P2O5 / K2O that will be approximately 1 / 0.5 / 1.5. In the phase of maturation and subsequent collection scalar ratio most used is 1 / 1.5 / 3 (water-soluble fertilizers such as ternary securities suitable 8-12-24 and 12-16-32), in alternation to single injections of potassium nitrate (use with caution) and calcium nitrate, which is useful to the improvement of the "hardness" of the fruits in warmer weather.
Field with vegetative material (fresh plants root "naked" and "top-rooted")
This type of plant is not going through a period of dormancy and early winter and go directly to the reproductive phase.
We will then post-transplant, similar to what is stated for systems with cold stored plants.
In the period from December to January you will have to carry on with fertilizer inputs, useful for the formation of the plant, using the solutions of balanced (1-1-1), not neglecting the contributions of phosphorus to encourage flowering, and then proceed to subsequent steps, such as for cold-storage plants, when you walk into the production phase.
The fertigations not go so never suspended, but only adopted for the development and production of vegetative plant.
Nutritional deficiency symptoms (physiopathological diseases)
The non-absorption of macro and micro elements, due to the dearth of soil or inducing factors such as high pH or excessive salinity, causing the characteristic symptoms borne mostly leaves (physiological disorders by nutritional deficiency).
Among the most frequent phenomena cites definitely the calcium deficiency that causes deformations and of the load of the apices foliar necrosis. During rapid leaf growth tip burn symptoms may appear on immature leaves. The tips of these leaves fail to expand fully and become black. Fruit develop a dense cover of seeds, either in patches or over the entire fruit, and develop a hard texture and acid taste (Figure 10). The roots become short, stubby and dark.
Figure 10 - Calcium deficiency. Leaf tip burn (left and centre). Small fruit with dense cover of seeds (left).
The control consists in to adjust the soil pH. Apply calcium in the form of agricultural lime or dolomite before planting. Apply calcium nitrate by fertigation or as foliar spray at first sign of deficiency.
Other symptom that often found in strawberry fields implanted on soil at high pH or when the irrigation water is alkaline it is the inter-veins chlorosis of the leaf due to iron deficiency. Yellowing and green veining are the first signs of iron deficiency. As the deficiency becomes more severe, yellowing increases to a point of bleaching and the leaf blades turn brown (Figure 11). Fruit size and quality are not greatly affected.
Figure 11 - Iron deficiency.
Alkaline or poorly drained soils can induce iron deficiency. Check soil pH levels. If the pH level is high, cease liming and use acid-forming fertilisers such as sulfate of ammonia. Apply iron sulfate by fertigation when symptoms first appear. Foliar sprays with iron sulfate or chelate can also be used.
Strawberries are among the crops that are very sensitive to salinity. Lack of rains earlier during this season has caused some concern about the impact of salinity on young strawberry plants. However, with the recent rains the total amount of precipitation for January, 2012 was about 2 inches (~50 mm) easing some of the concerns.
Symptoms of salt injury include dry and brown leaf margins (Figure 12), brittle leaves, stunted plant growth, dead roots and plants. When salt toxicity is seen in localized areas in a field, it could be due to poor drainage. Symptoms can be seen throughout the field when salinity of the irrigation water is high. Excessive fertilization or application to wet foliage can also result in salt toxicity. More than 0.2% of sodium or more than 0.5% of chloride in plant tissue indicate salt toxicity.
Figure 12 - Symptoms of salt injury by necrosis of the leaf margins due to excessive salinity of the soil solution.
Salinity of the irrigation water depends on the amount of sodium, calcium and magnesium salts. Salinity is measured either as total dissolved solids (TDS) or the electrical conductivity (EC) imparted by the salts. The latter is often considered a better measure of salinity and is expressed as the EC of the irrigation water (ECw) or the EC of the saturated soil extract (ECe). Units of measurement for are milligrams/liter (mg/L) for TDS and decisiemens/meter (dS/m) for EC. Other parameters for soil salinity are pH and the sodium absorption ratio (SAR). SAR is a measurement of sodium absorption compared to calcium and magnesium absorption and is used as an infiltration index.
Insufficient leaching of irrigation water in the soil is a major cause of salt accumulation in the root zone. When irrigation is made just to meet the plant needs, salts gradually build up in the root zone. It is important to provide sufficient irrigation so that water will wash the salts away from the root zone. The proportion of water that leaches below the root zone after meeting the crop needs is known as leaching factor (LF). The amount and frequency of irrigation should be calculated appropriately to allow sufficient leaching at the same time avoiding excessive soil moisture which could cause other problems.
Compared to the crops grown in hot and dry areas, crops grown in milder climatic areas such as California Central Coast are likely to tolerate higher salinities. Salts in the Central Coast area waters are gypsiferous with calcium and sulfate ions. Waters with such salts do not cause the same level of detrimental effects compared to water with chloride even when they have same ECw.
ECw (salinity of the irrigation water) is a better indicator than ECe (salinity of the soil) to measure the impact of salinity on strawberry or other crop yields in the Central Coast. There can be up to a 50% reduction in the yield potential of strawberries when the salinity increases from 0.7 to 1.7 ECw (dS/M) with a leaching factor of 15-20%.
It is important to look at the type of salt and kind of test being done to determine the salinity. It is also necessary to consider the leaching factor when scheduling irrigation. Sampling the irrigation water two or more times a year to test is recommended if salinity is suspected.
Strawberry Selection and Storage
With the flexibility of the growing seasons in Mexico, California and Florida, and importation from reverse-season areas like South America, strawberries are available pretty much year-round.
If at all possible, grow your own strawberries, allowing them to fully ripen before picking. Unlike some fruits, strawberries will not continue to ripen on the counter.
Most commercial varieties are bred for hardiness, both in the field and shipping, and are picked for shipment before they are fully ripe. This can result in a firm-textured and less flavorful berry.
Select bright red berries with their caps intact and green, not dry and browning. They should be quite fragrant. Smaller berries are usually more sweet and flavorful. Avoid soft, moldy and/or shriveled berries. Check the underside of the container and pass over any that show indication of juice from bruised or rotting berries.
Strawberries should be eaten as soon as possible, and do not wash until you are ready to consume them.
If you must store strawberries, place them on a paper towel in a tightly-covered container and store in the refrigerator for 2 to 3 days.
Strawberries are easily frozen. Gently wash them, dry, and remove the caps. Place on a cookie sheet and freeze. Once frozen, place in a zip-top bag, suck out the air with a straw, and seal. Return to the freezer for up to 6 months.
Strawberry Plant Propagation
Strawberry plugs are fast replacing traditional bare-root transplants in many parts of the world as growers recognize that container-grown plant material usually provides a better opportunity to control critical production factors that influence plant health, rate of transplant establishment, early yield, total yield, and fruit size and/or grade characteristics.
Plug production of bedding plants, vegetable transplants, pot crops, cut flowers, tissue-culture material, and trees has become a worldwide business. The number of plugs used in the U.S. and Canada is estimated to exceed 25 billion. In Europe almost all greenhouse vegetables and cut flowers are plug propagated.
In 1998, about 1 million large plug plants, also known as tray plants, were propagated in central Europe for glasshouse strawberries.
The commercial production of tray plants is expected to increase in the United Kingdom over the next few years.
In the mid-Atlantic region of the United States, plug plants are recommended for late August (New Jersey) and early September (Virginia) transplanting in the annual plasticulture system.
Despite higher costs for plugs compared to fresh-dug bare-root plants, plug use increased in North Carolina from less than 1 million plugs in 1992 to an estimated 8 million plugs in 1998.
Advantages of plug production technology
Finally, there are three main ways to propagate strawberry plants. The plants can be divided and transplanted once multiple crowns have been grown (or division of rhizomes), new plants can be grown from strawberry seeds, or the runners that strawberry plants put out can be controlled, guided, and caused to root where clone plants can be utilized most efficiently.
- Reduction in pesticide requirements and soilborne diseases. Strawberry plug plants are grown from unrooted runners called tips. The tips are directly rooted into specially designed trays that usually contain a peat based media, although direct rooting into rockwool propagation blocks is also possible. In a peat-based root media or rockwool, there is little likelihood of plugs becoming infected with verticillium wilt (Verticillium spp.) and/or Phytophthora root rot (Phytophthora spp.), unless the water supply is contaminated. The primary site of infection for Phytophthora is in the meristematic region behind the root cap. Stem tissues such as stolons are not avenues of infection. Therefore, runner tips are ideal propagules for avoiding transmission of these root invading diseases. Chemical methods of control for these diseases have only limited effect once symptoms of the disease are observed. In the U.S., methyl bromide plus chloropicrin (MBC) is the preplant soilfumigant of choice used by nurseries for the control of soilborne diseases, nematodes and weeds. Other chemical alternatives to MBC include dichloropropene 85% + chloropicrin (Telone C; Dow AgroSciences, Indianapolis) and metam sodium (Vapam; AMVAC Chemical Corp., Los Angeles). As governments around the world take action to reduce and soon eliminate methyl bromide soil fumigation, there likely will be greater scientific and industry interest in systems for producing runner tips and strawberry plugs that are not dependent on a soil propagation phase. Plug transplants are produced inno more than 5 weeks, and in warmer growing regions (e.g., North Carolina, Florida, Egypt) the process of propagating a strawberry plug that is pullable from the plug tray for transplanting can be as little as 3.5 weeks. This short cycle makes it less likely that plugs will have as many problems with insect-vectored diseases as fresh-dug transplants that are exposed to field conditions for about 4 months from spring planting until late summer/fall harvest. Significant damage from the spread of viruses and phytoplasmas can occur during this extended period of field exposure. Additional benefits of producing a strawberry transplant in 4 weeks as opposed to 4 months may include more selective uses of pesticides, reduced worker exposure to pesticides, and lower pesticide residues in strawberry transplants. Sanitary, pest-free plant material is particularly essential to greenhouse strawberry producers as no registered pesticides are available in the U.S. for greenhouse production.
- Ease of transplanting. Transplanting highly perishable fresh-dug plants is labor intensive, requiring up to 30 laborers/ha (12 laborers/acre). However, plugs can be mechanically transplanted, requiring a crew of only 5 workers to transplant about 0.6 had1 (1.5 acres/d),17,400 plugs, using a two-row plug transplanter. For a typical pick-your-own strawberry farm in North Carolina of only 1.2 ha (3 acres), the entire transplanting operation can be completed in 2 d. A mechanical transplanter can consistently plant each plug so that the midpoint of the crown is level with the soil surface. With fresh-dug plants, inexperienced planting crews frequently fail to set the plants at the correct depth resulting in poor plant performance or even death.
- Reduced water requirement. With fresh-dug plants, overhead irrigation must begin within 1 h of planting. These plants then require an intensive daily overhead-sprinkling schedule (from morning until late afternoon) for 1 to 2 weeks, depending on weather. Under hot, sunny conditions, it is beneficial to irrigate plugs for a few hours the day of transplanting. After the first day, plugs require very little, if any, overhead sprinkling. Water can be furnished to the plugs through the drip irrigation system following transplanting. This is a major benefit to the part-time grower who does not have time to oversee the daily overhead-sprinkling program needed for fresh-dug plants. It is also an important disease management strategy to minimize the use of any overhead irrigation after transplanting.
- Improved plant survival. Nearly 100% of plug transplants survive transplanting. With fresh-dug plants it is necessary to replace a significant number of weak or dead plants that do not survive the transplanting process. Plugs keep more root hairs, that quickly absorb water and nutrients. This active root system allows more uniform and faster plant growth after transplanting. Because of this faster initial growth, plug transplanting dates can be delayed by up to 5 d after the optimum planting date for fresh-dug plants.>
Industry uses of plug plants
- U.S. plasticulture production. To achieve full production, timely planting is one of the most critical aspects of growing strawberries in the plasticulture system. In the eastern U.S., fresh plugs are field transplanted in middle to late summer, or fall, depending on the production area. For the mid-Atlantic region, growers transplant plugs in middle to late August or early September to achieve full crops the following spring. By obtaining Chandler runner tips for plug propagation in mid-to-late July, strawberry growers in this region can be assured of having plants ready for field transplanting as early as mid-August for the plasticulture system. Fresh-dug bare-root transplants are not an option for growers in the mid-Atlantic region as northern U.S. and Canadian nurseries do not dig until after mid-September. Further south, in North Carolina, growers can transplant either fresh bareroot transplants or fresh plugs in September, or early October, depending on growing area. Fresh bare-root transplants and fresh plugs will produce comparable yields. In North Carolina, both fresh plugs and freshdug bare-root transplants have similar reproductive physiology, and will ripen about 10 d earlier than dormant-stored transplants that were planted in late August. In Florida, virtually all of the 2,350 ha (5,875 acres) of production is planted in bare-root transplants costing $0.07 to $0.08 each, corresponding $3,200 to $3,700/ha ($8,000 to $9,250/acre). The larger strawberry growers in Florida generally have access to relatively inexpensive labor for transplanting the cheaper fresh bare-root transplants. With delivered plugs costing $0.14, few growers in that state feel that spending another $3,200/ha, or more, for plugs is justified. However, temperature and/or photoperiodically conditioned plugs, that can have significantly higher early and total winter production in southwest-central Florida than bare-root transplants from the northern U.S., may warrant the higher establishment costs associated with plugs.
- U.S. greenhouse production. Artificial night chilling, with 4.5 °C (40.1 °F) from 1900 to 0800 HR for 15 cycles, enhanced fall and winter greenhouse productivity of plug plants derived form secondary and tertiary runner plants of Selva. Secondary plugs had higher early season fruiting compared to tertiary plugs. Conditioned plug plants were successfully used for winter greenhouse production in New Jersey. In one experiment, 2- to 3- week-old Sweet Charlie strawberry plug plants were conditioned, with 7 short days (9 h) without chilling (21/21 °C (69.8 °F) day/night)], followed by 7 short days (9 h) with chilling during the nyctoperiod with 21/12 °C (69.8/53.6 °F) day/night, in September, then planted in a vertical hydroponic system for winter greenhouse production. Conditioned plugs produced significantly more fruit than did non-conditioned control plugs in January and February, but the difference was not significant in March and April. Productivity over 4.5 months was 4.8 kgm2 (1.0 lb/ft2) for controls and 7.8 kgm2 (1.6 lb/ft2) for conditioned plugs. It was investigated the use of aquaculture wastewater as a source of water and nutrients for hydroponically grown plug plants of Chandler. Plants produced more than 600 g (1.3 lb) per plant from January through March and also effectively reduced phosphorus discharge from aquaculture wastewater.
- European plasticulture and greenhouse production. In central Europe, fresh Elsanta plugs are propagated for transplanting into field plasticulture by late July or early August. These plants will produce a main crop the following late May and June, or can be forced for 2 weeks earlier fruiting in May by covering the crop with a high plastic tunnel. A portion of the maiden year plasticulture beds in the U.K. may be deep strawed for delayed fruiting after the main season when lower volumes of Elsanta on the market can lead to significantly higher prices. Runner tips of Elsanta can be readily obtained in midsummer from a variety of propagators in central Europe and the U.K., or from specialized runner tip growers in southern Portugal and Spain. In the U.K., a limited number of commercial producers are also establishing field nurseries with Elsanta plugs in late July and early August. The transplants are allowed to develop in the field until being lifted (dug) in December when there has been an accumulation of 500 to 600 h of temperatures below 6 °C (42.8 °F) and/or before a hard frost. Transplants are then either planted in the glasshouse, or placed in cold storage at 1.5 °C (29.3 °F). Plants are graded as waiting-bed plants at 17 mm (0.7 inches) crown diameter, or A+ plants at 15 to 17 mm (0.6 to 0.7 inches) crown diameter. Nongraded field-conditioned plugs are also dug and stored. In recent years there has been a move to commercial strawberry tray plant production in parts of central Europe where conventional bare-root waiting- bed and A+ plants for glasshouse strawberries have now been replaced by tray plants. Tray plants have the potential to produce Elsanta fruit of very high cosmetic appearance and often produce higher yields and larger fruit than a similar size frozen A+ bare-root plant, partially offsetting their extra cost. Waiting-bed plants have been used for winter production in Spain. Productivity of four cultivars was influenced by the number of crowns (one to five) each plant had at planting. Oso Grande was most productive with two crowns per plant, Vilanova and Pajaro were most productive with three crowns per plant, and Chandler was most productive with four or five crowns per plant. Winter production in both high and low tunnels in Turkey has been reported. In one study, plugs planted in August produce fruit by early November while frigo plants set at the same time did not produce fruit until the following February . In another study, both types of plants set in the field in July did not fruit until February. Later fruit production (February onward) was associated with frost injury to flowers in November and December (Figure 13, 14 and 15).
Figure 13 - Detail of the EC passport on a case of cold stored plants certified.
Figure 14 - The plants are uprooted during dormancy and packed in wooden boxes (left) to be subjected to cold storage at -2 ° C. The bunches of rooted seedlings are then transplanted (right).
Figure 15 - Bouquets of plants cold stored, ready to be transplanted.
- Plug plant production. Plug propagation is divided into several stages beginning with the production of unrooted plantlets on the tips of runners, and ending with a fully rooted plug that is ready for shipping, transplanting, special conditioning or holding in cold storage.
- Runner tip production. The first propagation step is to generate a supply of fresh runner plantlets commonly called tips. A common approach in Canada is to grow the tips from California-nursery- registered stock plants that are transplanted in double rows with 43,000 plants/ha (17,200 plants/ acre), on fumigated, raised beds that are covered with black plastic mulch. With this system in southern Ontario, the first runner tips are harvested in just 8 to 10 weeks after planting in early June. Fresh tips of the popular eastern cultivar Chandler are commercially harvested from the end of July through the first week of September. Tips are harvested at frequent intervals (two to three times per week, depending on temperatures) to provide greater plant-size uniformity. Potentially, a higher yield of stolons and daughter plantlets than 10:1 could be achieved if the tip nursery was not harvested so frequently. But, the market in the mid-Atlantic region and North Carolina dictates that the runner tips are harvested frequently to keep the plantlets within a relatively narrow size range. Recommended specifications for runner tip propagators are as follows:
- Stock plant material. Use only certified stock that is free of disease causing virus, fungi and bacteria.
- Number of intact leaves. Two trifoliate leaves are needed. The leaves should not be trimmed, or cut off . The petioles must not be injured.
- Height of oldest trifoliate. Nutrition, watering and cultural practices should be tailored to produce a plantlet that does not have the older trifoliate extending more than 10 cm (3.9 inches) in height from the base of the small crown.
- Grading by leaf height. There is an acceptable range in plantlet size with the oldest trifoliate measuring a minimum of about 6.5 cm (2.6 inches) up to 10 cm (3.9 inches). Tips that are larger or smaller should not be harvested for plugs.
- Crown diameter. 20 to 50 mm (0.8 to 1.9 inches) (more research needed).
- Stolon attachment to crown. 1 to 1.5 cm (0.4 to 0.6 inches) section is ideal for anchoring the tip in peat-based soil or rockwool media. Some research indicates that stolon diameter of 4 mm (0.15 inches) is preferable to 2 mm (0.08 inches) for earliest floral initiation.
- Root system. Plantlets are too small for harvest and plugging if there are not several peg roots, or root nodules formed (rooting success will be limited without peg roots). The plantlet is not as desirable for rooting if the peg roots are dark (should be whitish) or if roots more than 1 cm (0.4 inches) have been expressed. There should be no soil particles attached to the plantlet. In Belgium and the Netherlands the preferred system for producing runner tips for tray plant production is to plant frigo stock plants in plastic peat bags that are placed on top of a white polyethylene film-covered-bed (to prevent tips from contacting soil), and the aisle area is covered in wheat straw. The stolons spread horizontally on the wheat straw, and are harvested as tips in mid- July. Suspended systems for growing tips generally have been abandoned in central Europe because of shading problems that causes a premature transition from a vegetative to a floral meristem. Additionally, the upward orientation of the 1 to 1.5 cm (0.4 to 0.6 inches) stolon section attached to the base of the young plantlet makes it impossible to use this stub for anchorage of the runner tip in the cell module.
- Rooting. Most commonly a greenhouse or plastic tunnel is used for rooting runner tips under mist. An enclosed structure is needed to prevent damage from high wind and/or heavy rain. Shade houses can be used, but these structures are usually ineffective for wind and rain control. In addition, light levels under shade structures will be insufficient after the first week of rooting. Strawberry plugs also can be produced inexpensively outdoors. The plug trays are placed on top of woven polypropylene ground covers and are then covered on top with a thin white polyethylene film. The white plastic film reduces radiant heat, and provides a humid environment under the tarp to prevent wilting of the perishable runner tip. Difficulties with this method often relate to having too much covering during the first 2 weeks of rooting and new leaf development. When the weather is cloudy and rainy for several days, plugs will stretch because light levels are too low. It is also more difficult to regulate moisture underneath plastic tarps, and in cool, overcast periods; grey mold (Botrytis cinerea) will readily spread from weak plant tissues and fresh plant debris to healthy leaves under such conditions. Little published work exists on the effects of tray construction (styrofoam, polyethylene, polypropylene), cell sizes (small, medium, large), and cell configuration (plugs may be round, square, hexagonal, octagonal, or star-shapes) on strawberry plug rooting amount, root quality, and plug pullabililty for transplanting. There is some literature that addresses questions related to the interaction of the medium with strawberry plug size and geometry. The root dry mass and root branching of Sweet Charlie plug transplants fertirrigated on a capillary mat for 4 week was highest in a 150-cm3 (9.1- inch3) container volume of 6.5-cm (2.6- inch) cell depth, and 0.31 to 0.43 cm (0.12 to 0.17 inches), particle size vermiculite. In North Carolina, the general commercial practice is to use a non-reusable, round, straight-sided, 50-cell, polyethylene tray with 5.7 × 27 × 53 cm (2.2 × 10.6 × 20.9 inches), costing about $0.40 each. Plug trays are usually filled by hand with a commercial plug mix that contain peat, vermiculite and some amount of composted pine bark, processed bark ash and washed granite sand. When placed in a 5.7-cm (2.2-inch) deep tray, it is common to have about 6% air space and 75% water content. About 5 L (1.3 gal) of mix is needed per 50-cell tray (about $0.50 per tray). The plug mix must be moistened before sticking tips and the trays should not be nested directly on top of each other to avoid compaction. Well-produced runner tips require no additional preparation before rooting, and can be taken directly from the box without additional size grading and trimming of stolons. An approximate 1.5 to 2.0 cm (0.06 to 0.08 inches) runner stub serves to anchor the plantlet until new roots develop, within 48 h new roots of 3 to 4 cm (0.12 to 0.16 inches) in length usually penetrate the plug mix. An intermittent-mist water spray over the leafy tips is the most effective way to root strawberry plugs. The initial rooting stage under mist requires about 7 to 10 d. In the first few days under warm sunny conditions it is advisable to mist more frequently (10 s of mist every 5 min). After the first few days it is usually satisfactory to mist for 30 s every 12 min. The goal is to gradually decrease the misting period as new roots develop by lessening the on period and increasing the off periods, or by leaving the misting intervals the same but gradually decreasing the time for which the mist is in operation each day. Misting is usually terminated by day 10, but under some circumstances it may require 12 d. For the next week the plugs are watered regularly, and by the end of the third week the plug trays can be moved into full sun for weeks 4 and 5 (if needed). The trays may be placed on top of woven polypropylene ground covers or a nursery gravel pad for the final week or two of outdoor hardening. By week 4 or 5 the plug is ready to be pulled from the tray for transplanting without the media falling off the roots.
- Conditioning. Before transplanting, the strawberry plug can be manipulated, or conditioned, for glasshouse forcing in winter or for earlier winter production in regions with moderate temperatures (e.g., Florida, Southern California, Israel, and Egypt). Short day (SD) low-chill cultivars are good candidates for conditioning programs in areas with moderate winter temperature conditions and photoperiods of less than 14 h. An extensive amount of research was done in the mid-to-late 1980s to identify cultivar specific photoperiodic and chilling requirements in potted transplants of Douglas, Pajaro, Chandler and Tufts. More recent investigations have focused on preconditioning plugs of commercially popular SD-low chill cultivars (Sweet Charlie, Camarosa) for an earlier winter ripening period (when prices are normally higher). Over 10 years ago, was demonstrated that the SD low chill cultivar Douglas grown in 10.5- cm (4.1-inch) plastic pots in a North Carolina nursery responded primarily to photoperiod for enhanced early fruiting in Florida winter plantings. While the transition from a vegetative to floral meristem in Douglas is rapid (about 14 SD photoinductive cycles at 9 h daylength), an additional 14 cycles were needed to optimize flower buds and/or increase floral initiation. The number of SD photoinductive cycles for optimum early yields could be reduced with night chilling at 4.4 °C (40 °F). The photoperiod response varies with cultivar and chilling. In Pajaro and Douglas, chilling accentuated the photoperiod effect and enhanced early yields. In Chandler, low levels of chilling (<125 h) reduced early yield while higher amounts (>125 h) enhanced early yield. The conclusion that the initiation of flower buds is controlled primarily by photoperiod and to a much lesser degree by temperature was further supported by more recent investigations. Three-week-old vegetative Sweet Charlie and Camarosa plugs were exposed to 8-h short days for 1, 2, or 3 weeks at either 10 or 16 °C (50 or 60.8 °F) night temperature and 22 °C (71.6 °F) day. Short day conditioning of plugs in weeks 4, 5, and 6 before transplanting in Florida (24 October) significantly enhanced early (December) yield in both cultivars. In another investigation of conditioning, 3-week-old Sweet Charlie plugs conditioned for 2 weeks at 25/15 °C (77/59 °F) day/night temperatures flowered earlier and had higher November and total yield compared to plugs conditioned at 35/25 °C (95/77 °F) (Bish et al., 1997a). However, the photoperiod effect was not investigated. The optimal daylength for floral induction in SD cultivars is generally between 8 and 12 h, but the role of photoperiod is more critical at temperatures above 15 °C. It is possible that the natural photoperiod in Dover, Fla. during this temperature conditioning (from 19 September to 3 October) was satisfactory (short enough) for floral induction at 15/15 °C, but not for the warmer 35/ 25 °C day/ night temperature condition. Clearly, in plug conditioning investigations, photoperiod and temperature both must be investigated if the goal is to optimize conditioning parameters to induce precocity and enhance yield. The general fruitfulness of SD low chill strawberry plugs and potted plants can be managed by controlling the length of time plants are grown under short days, and that dark period chilling of 4.4 to 10 °C (40 to 50 °F) during floral induction can enhance total yield for certain cultivars. However, more research is needed to understand the critical photoperiod requirements of newer low chill or no chill SD cultivars (i.e., Sweet Charlie) and how warmer temperature treatments (i.e., 35/25°C day/night) may influence the number of SD cycles needed for floral induction.
- Storage. Runner tips are generally cut and graded in the field and then moved quickly to the cooler 0 to 1 °C (32 to 33.8 °F), 95% relative humidity. Tips are frequently collected under warm to hot conditions in southern Ontario (July, early August), and it is essential to remove them from the field as quickly as possible, preferably in 45 min or less. The tips should be cooled to 0 °C. A good cold chain from the runner tip producer to the plug grower is essential for best rooting success. The temperature of tips should not be allowed to rise above 2 to 3 °C (35.6 to 37.4 °F) in transit. Well-handled runner tips have a safe storage life of up to 1 week, but every reasonable effort should be made to root the runner tips as soon after harvest as possible. Tips may be safely held in a cooler at the plugging location for a few days at 3 °C. Tray plants have cold storage properties that are better than bare-root waiting-bed plants. They provide more rapid and even establishment under hot midsummer conditions under glass than similar size bare-root A+ plants. When dormant, the plants can be removed from the trays and placed in cold storage at 1.5 °C (29.3 °F) for up to 8 months.
- Shipping. Properly grown tips are compact in size and 1,000 tips with box and liner will weigh about 5 kg (11 lb). As a result, runner tips are economical to ship by air freight. The greatest expense for growing runner tips is for hand labor to collect and pack the tips. Transportation costs for shipping tips are very low relative to shipping a finished plug, or fresh-dug bare-root transplant. A box containing 1,000 compactly grown strawberry runner tips shipped from Ecuador to Miami, for example, will have freight charges for air shipment that average less than $0.005 per tip. Local shipment of finished plugs from the plugging greenhouse to area growers is easily accomplished with flatbed trucks. Specially fitted trailers with plugtray carrying racks are needed to transport large numbers of plugs greater distances. A common carrier tractor trailer in the U.S. equipped with racks can hold about 1,200 50-cell trays (60,000 plugs) at a cost per plug that is roughly three times higher than shipping costs for a runner tip.
There are positives and negatives about propagating strawberries with each method, all of which will be briefly discussed. However, to offer the bottom line up front, most gardeners will find that the easiest way is to propagate strawberry plants by runner.
In conclusion, container-grown strawberry plug plants offer an important alternative to conventional field-grown strawberry transplants. Strawberry plugs are grown in controlled environments (greenhouse, tunnels) in less time than field produced bare-root transplants, and are not exposed to soilborne pathogens (Figure 16).
- Strawberry Propagation by Plant Division. Many types of strawberry plants will, either by nature or if encouraged by pruning runners, put out lateral crowns at the base of the strawberry plant. These lateral crowns can be divided and replanted to propagate strawberry plants. Additionally, the genetically generative rhizomes of strawberry plants can, under the right circumstances, be divided into multiple pieces with each piece being sufficient to grow a new plant.
There are, however, several drawbacks to this type of strawberry propagation. Often, the mother plant will be compromised (if not done correctly) and will die. Thus, the net increase of strawberry plants is diminished. Also, it tends to be more labor-intensive and technical as the division or cutting takes both precision and a bit of expertise. However, for well-funded or commercial operations, this division can be used to propagate cloned plants quickly and extensively.
- Strawberry propagation by planting strawberry seeds. Growing strawberries from seeds has the potential for vast numbers of new strawberry plants to be grown. Each strawberry has approximately 200 seeds adorning its outer surface. While unusual for every seed to be viable, that is still a lot of new plants from a single strawberry. Starting strawberry seeds will require most of the standard seed-starting equipment to be used. And, while starting strawberry seeds often requires a few more considerations than does starting common garden vegetables from seeds, it is not overly difficult.
The major drawback of strawberry propagation by seed is the nature of todays common strawberry cultivars. Once the Garden Strawberry (Fragaria x ananassa) became the dominant strawberry grown in both home gardens and commercial operations, the seeds became unreliable due to the crossbreeding used to obtain the improved strawberry varieties. This means that attempting to grow strawberry plants from seeds that were collected from a purchased strawberry will likely not produce true plants. In other words, the plants grown from seed will be different from the plant that produced the seeds (sometimes substantially so). The seed-propagated strawberry plants will exhibit genetic traits of the grandparent plants instead of the desired parent plant. The wild strawberry species are an exception to this and will produce plants true-to-form. However, their fruits are much smaller, in general, and not recognized by most as the strawberries that are commonly bought and consumed today.
- Strawberry propagation by runners. Growing strawberry plants from a runner is, for most, the easiest and quickest way to propagate strawberries. Most of the June-bearing, ever bearing, and day-neutral varieties produce runners. Some of the wild strawberry varieties do not and must be propagated by seed. But, in general, if someone buys a strawberry plant, it will produce at least a few runners.
Figure 16 - Alveolar polystirene containers with plants in "top-rooted" ready to be transplanted in the greenhouse (not yet covered) on soil equipped with perforated black mulch.
Plugs afford greater grower control of transplanting dates, provide mechanical transplanting opportunities, and allow improved water management for transplant establishment relative to fresh bare-root plants.
New uses for plugs have been identified in recent years, including earlier flowering and fruiting with conditioned plugs, and in glasshouse production. In time, labor issues and prevailing environmental concerns throughout the world may increase interest in strawberry plugs, but higher prevailing costs for this propagation method is limiting current plug usage to specialized niche applications.
The scientific community has an opportunity to improve industry adoption of plug plants by developing more cost-effective methods for producing large volumes of disease-free runner tips, and improve the evenness and growth of plug plants in the tray and thereby achieve more uniform growth and fruiting after transplanting. In the future, scientists may learn to inoculate strawberry plugs with various performance-enhancing agents and possibly reduce plug size for savings in media, plastic trays and greenhouse space. Exposing plugs to different natural environments for meristem conditioning effects can advance flowering and fruiting, but plug trays are bulky and expensive to move.
Researchers need to identify less expensive means to condition strawberry plugs, preferably on one site. Finally, well-coordinated efforts between horticulturists, engineers and industry, could lead to useful applications of robotics in strawberry runner-tip harvest, plug rooting, transplanting and conditioning.
Transplantation should be performed on mulching film of 1.40 m in width. Once you have determined the distances between plants, as described below, the farm may obtain supplies of mulch
prefored or to perform the holes once the film is laid on the soil plot, as shown in Figure 17. The operation of the transplant in greenhouse is carried out manually.
Figure 17 - Building of the greenhouse to transplant strawberry. If the greenhouse is built as shown with a certain advance at the time of transplantation (for example in mid-July), the time between the start of greenhouse construction and the start of the transplant may give rise to a valid solarization which represents a valid natural disinfection method of the soil.
About the planting density, is preferred to adopt the twin row in staggered rows. The trasplants are normally set in double rows with plants spaced 25 cm in-the-row by 30 cm between the row for cold-storage plants and tops rooted plants, that have greater vigor. This values are variety-dependent and the longer distances have to be taken to the more vigorous varieties.
If you are using fresh plants to bare root, less vigorous compared to the cold-storage plants and the tray plants, the distances in the row can be reduced to 15-20 cm.
The investments are traditionally conditioned by the distance between the swaths (1.2-1.5 m), which varies depending on the personnel experience and the local pedo-climatic conditions. It should be from 40,000 plants per hectare generally planted in cold-storage plant cultivations under small tunnel, up to density of 60,000-80,000 plants/ha of fields with fresh plants under multi-tunnel.
Were also evaluated plants with single rows (15 cm between plants), but they have not found widespread use.
About the time of transplantation, it must be said that this is done at different times depending on the type of plant used and the type of greenhouse and the tunnels:
The plants before they are planted, should be treated with authorized fungicides can control the pathologies of the roots and the collar.
- for cold-storage plants and for a protective structure represented by small tunnel, tunnel or greenhouse-tunnel: the transplant is cariied-out from mid to late September;
- for fresh plants to "top-rooted" and for a protective structure represented by a greenhouse-tunnel: from September to October;
- for fresh plants to "bare root" and for a protective structure represented by a greenhouse-tunnel: the transplant is carried-out in October.
Traditionally transplantation is performed in the field, while the coverage of the structures of forcing takes place at a later time.
When working in a greenhouse-tunnel, with cover sheet three years during, you often find yourself performing the transplant in structures already covered. Therefore, essential to best treat the phase of engraftment, ensuring a constant wetting of the substrate and the moisture control indoor relative, through continuous sprinklings or nebulisations.
Modernization of the transplanting
Forms and structures of forcing
The continuous evolution of cultivation techniques has made it possible to upgrade systems to forcing. Such systems, starting from the first productions in the field, have evolved in the traditional small tunnel (still used today), up to modern modular multi-tunnel.
Period of coverage of protective structures: as already said, the transplant is performed in full field, with the exception of the plants under greenhouse-tunnel covered with sheet to long-term duration. The coverage of the cultivation is carried out, in general, after overcoming the crisis of transplantation or at the end of the first phase of vegetative growth. The time in which this is done differs greatly, depending on the type of plant, the structure of forcing and the season performance. In Table 6 provides a statement summarizing of the maximum.
- Small tunnel: these are structures of semi-forcing, with arches made of iron rod supporting the cover film; the fabric is anchored to the twine through arches which allow to adjust the closing and opening of the small tunnel (Figure 18).
Figure 18 - Small tunnels under that the strawberry is cultivated.
- Greenhouse-Tunnel: tunnels are designed to withstand a wide scope of weather conditions such as wind, snow and high temperatures. The
body is made of galvanized steel pipes as per international standards Z275. The width of a greenhouse tunnel ranges from 4.5 m, 8.0 m
or 9.0 m and does not exceed 61.5 m in length, with a maximum 3.2 m height. All metallic profiles and tubing are galvanized
with 275 gr/m2 zinc coating protection G90 through a continuous procedure to meet the quality requirements according to Sendizmir
procedure. The pillars and doors are hot dipped galvanized. Available in a wide variety of heights and widths (Figure 19).
Figure 19 - Tunnel for strawberry protection. Note the double cover sheet which, acting as insulation reduces the temperature range inside (left). The greenhouse-tunnel is larger, with simple arches (center) and reinforced with arches (right).
- Multi span greenhouses (Figure 20): it is a group of tunnels interconnected to form a large undercover area where a typical bay length is 39 meters
duplicated into several bays. A standard model has an area of 702 m2 with the ability to be expanded by adding more bays. The body
is made out of galvanized steel pipes as per international standards Z275. The height of the bay ranges from 4.0 to 4.2 meters. There are
2 to 3 doors per unit depending on the work requirements. Multi -span greenhouses come with different ventilation / cooling openings
either in the roof, or a half moon opening at the front and back, or at the sides. It is also offered with a complete heating or cooling
system. The climate can be controlled with a specially designed software in case of automatic climate control systems.
Figure 20 - Internal (top) and outer (bottom) of a multi span greenhouses. The side, front and the ridge that can open, manually or automatically, for the purposes of the air turnover and thermo-regulation of the cultivation environment.
| Tabella 6 - Schema riassuntivo circa le epoche di copertura degli apprestamenti per la coltura protetta della fragola.
|Kind of plant
||Type of protective structure
||Time of coverage
Greenhouse tunnel - tunnel
On the first decade of January
Fresh with "bare root"
Grrenhouse tunnel - tunnel
Immediately after transplant
Fresh with "top-rooted"
One month after transplant
It is important to know how to transplant strawberry plants correctly so that they arent unnecessarily damaged and the stress to the transplant plants is minimized.
Cover materials: for covering greenhouses and tunnels should be used the sheets "thermal" containing EVA (0.15 to 0.20 mm thick), which guarantee better "greenhouse effect". It is recalled that EVA is ethylene vinyl acetate and it is a plastic copolymer of ethylene and vinyl acetate.
- Prepare your new location first. Make sure it is hospitable, sunny, rich, sandy loam, well-drained with slightly acidic soil, generally well-suited for strawberry plants, and historically acceptable (see the Growing Strawberries page linked above for more on the best growing conditions and soil-history concerns).
- Select the strawberry plants you will be transplanting. Generally, it is best to transplant established, young runner plants that are only a few months old. Choose only strawberry plants that look healthy, and remove any flower buds, damaged or discolored leaves, and runners prior to transplanting.
- Obtain a substance or material that will hold moisture. Sphagnum or peat moss is probably best, but something as simple as wet paper towels is usually sufficient. It is very important to keep the roots of your transplant strawberries moist during the transplanting process.
- Dig up your selected and prepared runner plants (or other strawberry plants). Take care to remove as much of the strawberry plants roots as possible from the ground (so that most of the roots are attached to the plant). Once free of the ground, cover or wrap the roots with your moistened peat moss (or other selected moistener).
- Transplant strawberries to your new, prepared strawberry bed. Do not dig up all the selected strawberry plants at one time and then try to plant them all at one time. Transplant one strawberry plant at a time. After each plant is in the ground at its new location, water it thoroughly before transplanting the next selected strawberry plant. This minimizes stress and increases the probability of success. Waiting until all the plants are transplanted before watering all the transplants simultaneously with a sprinkler or other apparatus may cause unnecessary plant loss.
For small tunnel we use a polyethylene sheet (0.10 mm thick). The sheets may be additives for the duration, to the effect dripless and for the degree of light diffusion.
Wintry cleaning (grooming) of the strwberry field: practice essential only for plants with cold stored plants; it is performed when the crop is in full dormancy. This is to remove most of the leaves and, in particular, those debilitated and dried, thus allowing the faster renewal of the vegetation at the end of winter stasis. This is typically done by hand or with grass-cutting suitably modified, allowing the elimination of the leaf older without compromising the central bud of the plants. It is essential to move away from strawberry field and destroy the plant material removed, which allows to reduce the load of pathogens and pests such as spider mites present on the crop and to better manage the pest management strategy.
Immediately after this treatment may take the winter against the red spider and copper-based preventive interventions against some cryptogams (leaf spot and other diseases).
Fresh plants "bare root" you do not do the shaving winter because this type of plant does not have to stop growing in winter.
The tray plants (most vigorous that the "bare-root"plants), while not requiring a real wintry cleaning, take advantage of periodic operations of stripping, with elimination of basal older leaves and consequent aeration of the plant.
Aeration: it need to put the utmost care with respect to this practice, which avoids excessive stress to the plant, favors, in the period of flowering, good fruit, limits the percentage of malformed fruits and creates an environment unfavorable to the development of diseases fungal infections, such as gray mold and powdery mildew.
The multi span greenhouses and the greenhouse tunnel can be ventilated with ease thanks to the large internal volume and the possibility of lowering lift the head walls and side (Figure 21).
In cases of early raising of the temperature and of the formation of excessive condensation, the drilling operation must be anticipated in early March. Regarding to the small tunnel from the beginning of the flowering stage it is necessary to intervene with the operation of daily diurnal opening (on sunny days and little windy) and closed at night, at least until in that the climatic situation stabilizes.
Figure 21 - In this modern greenhouse tunnel the heads and the side walls are raised manually or automatically to allow aeration.
Regarding the traditional tunnel, a good practice is reduce the length and provide a progressive drilling of the cover sheet (Figure 22).
Figure 22 - Tunnel with perforated sheet to allow, in a progressive manner with the increase of the outside temperature, the aeration.
Whitewashing the greenhouses and tunnels: it is the progressive whitewash of the cover sheet of the greenhouses and tunnels to reduce the internal temperatures and the relative humidity changes. It can be used the simple white lime or, alternatively, of washable paint or other specific products present on the market.
This practice exerts its positive effects if it is ensured at the same time a good management of the air turnover (Figure 23). You have to start early on this, when the sun radiation and thus the internal temperatures become excessive, with simultaneous lowering the relative humidity.
Figure 23 - Tunnel after whitening, to reduce the insolation inside, and after the drilling of the sheet of the lateral wall and the frontal opening of the greenhouse, to induce the aeration.
The time of start harvesting will depend on the type of plant used, from the protective structure,
the variety and the season trend. The operations are carried out in order
only manually, to the max with the facilitation of special carriages
for the transport of the boxes along the rows. The specialized labor used for the collection and other farming operations is ensured typically by family members and / or employees of
Here follow some recommendations to consider in the collection phase of the strawberry:
Strawberry is a delicate fruit and perishable, so the delivery of consignments of fruit to the conferral warehouse
be carried out in the shortest possible time. This avoids deteriorations
quality of the fruit and quickly enter the fruit in the cold chain.
The farmer in this phase must also:
- The harvest is an important step to make the best quality of strawberries because,
through repeated intervals, you can catch all the fruit to the right stage of ripeness
- It should be done by hand in the cool hours of the day. Then break in the heat hours.
The strawberries are picked in the morning and conferred as soon as possible to the warehouse for the sale.
- The empty primary and secondary packaging of should be stored in an appropriate way, in a clean area without
contamination by pests.
- Given that, in addition to the harvest, also the selection and the first packaging of the fruit
engaged directly in the field, you must inform the staff of the hygienic precautions
to be taken by going to direct contact of the fruit.
- Containers filled with harvested fruit should be protected from the direct sunlight and, if
possible, from excessive heat, moving them away from the field and storage them in shaded
and fresh towels or using shielding.
The cold-storage plants guarantees generally more abundant productions (also
800-1,000 g/plant), but more later or concentrated in a limited harvest period; the
quality (size, hardness, held to overripe) also tends to decrease with
progress of the harvest season. The introduction of varieties more qualitatively valid,
less prone to defects in pollination and equipped with a better shelf life are
bringing attention to the plants with cold stored plants, which seem to be able to
provide a productive response best suited to the very traditional Regional market
which caters almost all of the production.
- cure the cleanliness and hygiene of the vehicle used for delivery;
- prevent the transport of fruit together with other goods;
- avoid possible warming and the contamination of fruit during transport, covering the boxes of strawberries and making sure that the protection does not hurt.
The fresh plants, compared with a production that is often more quantitatively
The market concentrated in April and May does not seem to remunerate satisfactorily
production early, when these exceed the domestic demand, which appears
- growth rates slower,
- flowering early,
- more balance between vegetative growth and reproductive activity,
- anticipated productions (reduction of the period of anticipation) and staggered over a longer time,
- fruits higher quality and more constant throughout all the harvest period.
Before concluding the cultivation technique Strawberry is essential to treat the topic of the mechanization of cultivation work:
- Mechanization of mulch: the adoption of the technique of mulching has benefited mainly agronomic and environmental: 1) weed control; 2) reduction in the frequency irrigation with consequent cost savings; 3) most soil heating with early entry into production of crops; 4) harvested product already cleaned from the soil.
The sheets mulching (usually consisting of polyethylene) are arranged with common machines film-stretch which generally in one step determines the surface arrangement of the soil in addition to roll out the hose for irrigation and tucking the sheet itself.
The machines to roll out the mulching film are simple equipment, connected posteriorly to a machine (transplanter) or independent (manually mulching or motorized) that rolling out and tucking the film to the soil edge. Currently, there are many materials, including biodegradable ones seem particularly interesting. The plastics are different, but is mainly used polyethylene (PE).
Polyethylene (PE) is used on the market in different forms, in different colors and different thicknesses; especially in recent years are emerging on the market other products to replace traditional ones blacks or transparent.
For all the PE film is planned the hole to be indicated at the time of purchase according to the distance among plants chosen. The duration of the crop in the field, given that the material is hardly reusable, indicates which thickness is the most appropriate, although an important role is played by the ease of harvest at the end use. These sheets have different characteristics and, therefore, are used in a different way.
- Black (UV stabilized);
- Fumé (to different degrees);
- Photoselective Brown;
- Milk White;
- Green translucent;
In relation to other synthetic materials used in agriculture must be said that some years are marketing different synthetic degradable mulching materials.
- Black: excellent containment of weeds, not being permeable to infrared light, does not have any activities in advance of production and protection to the frosts. Also in hot climates may promote sunburn crop.
- Transparent: behaves in reverse way, low or no containment of the weeds, which remain below the film, allows an advance of the production and partial protection against frost; crops that grow on this mulching film does not "scald". The black and white film has the characteristic to contain effectively weeds, prevents the risk of sunburn and away some insects, especially aphids (such as silver cloth). It also guarantees a certain precocity and a higher yield of photosynthetic plant. All other types of colors have characteristics intermediate between those described above.
Although synthetic materials they have the ability to be degraded, but not biodegraded (if not in part) and, therefore, at the end of the crop cycle is impossible to remove them from the ground, resulting in non-compliance with the recycling of pollutants "special waste ".
The polyvinyl chloride (P.V.C.) is not recommended. While not explicitly prohibited in organic farming, but releasing pollutants into the soil and crops, is not contemplated in the technical means used. In addition, several private brands of organic (AIAB Warranty, Warranty and other biological AMAB) expressly forbid it in their production specifications.
Among the materials biodegradable cellulose (paper) we have:
Since the experiences provide for these materials a duration in the spring period of 50-60 days, but with the serious drawback of easily breaking at the point of planting, it must limit the use in a short cycle of vegetation or crops to facilitate sun the early stages of plant growth (unsuitable strawberry). It is possible to condition the duration, varying basis weight or thickness. They have a good weed control, but do not possess the property of being able to "anticipate" the maturation of the productions. The film is easily degraded by microorganisms in the soil; being biodegradable is not necessary to remove at the end of the crop cycle.
- Color havana;
- Color black (like crepe paper);
- Other colors.
The corn starch (Mater bi) is a film which has characteristics of elasticity and resistance comparable with the PE film, but has a duration, in the field, variable between 2 and 3 months. It is biodegradable and therefore should not be removed at the end of the cycle. Currently on the market can be traced only one colored black.
Viscose Film is composed of biodegradable fibers of vegetable origin. It has a duration of about 3 months, variable in function of the climatic conditions and the microbiological fertility of the soil. The fabric is supplied preseminato, even with seed provided by the manufacturer, and is well suited to the cultivation of vegetables from leaf especially in a protected environment and with good availability of water, particularly in the early stages of germination. It is effective in weed control. You traceable normally white, but you can take black.
There are pre-seeded types (virens), as "Viresco", made of 100% viscose cellulose white, breathable and water-permeable, in the plot containing the seeds of a crop. The cloth is available preseminato precision for the main vegetable crops. For its use is sufficient to prepare the ground normally, roll it and then lay the fabric with seeds facing up, making it adhere well to the ground with the first irrigation. After installation, flush repeatedly for the first few days, because you need to keep the biotessuto always moist during germination, until the complete emergence of all the seedlings. Then he irrigates as needed, as a traditional crop The cloth is then biodegradable in a time ranging from 2 to 4 months depending on the climatic conditions.
- Processing primary of the soil:
- Ploughing: this type of intervention, having regard to its nature, it should not matter some basic parameters including the status of the soil should be worked in excellent water conditions; the working depth which is important both for environmental and economic reasons, in the first because you bring to the surface layers and asphyxiated with a limited availability of nutrients in addition to move down organic material that is unlikely to be degraded adequately. The economic reasons are fundamentally linked to the increased demand for power to carry out the work; with crop residues or contributions of soil is recommended machining deeper.
To this culture is still advisable oscillating about a depth of 30 cm, which is desirable when possible the use of plows polivomere in order to limit the number of steps on the soil.
Following are recommended steps possibly with harrows (harrow teeth rigid, rotating disc) to refine the soil.
The practice of plowing is desirable, particularly when it is done is created a working soil and the soil presents the conditions of water stagnation, known to be deleterious for the crops in general and for this in particular. It would be desirable to perform the primary processing of the soil at least one month before the transplant.
You can use moldboard plows, disc plows or mechanical digger.
- Fertilizer: it is important to remember that given the Nitrates Directive No. 91/676 / EEC published in the Official Journal No. L 375 of 31.12.1991, the distribution of soil or fertilizer that will bring more than 170 units of nitrogen per hectare per year. Starting from the bottom of fertilization is usually performed by distributing manure or compost with the help of special sites (manure spreader and spreaders), then you can operate with different outfits depending on the type of product to be distributed, in particular you can refer to sprayers rod and suitable irrigation systems for the distribution of liquid fertilizers.
For the organic strawberry there are no particular information on the type of nutrient to be used if not obviously those allowed by Annex 2A of reg. 2092/91 and whose use is authorized in Italy.
Must also be assessed by the ability to make the green manure with type functions improver, in this case, the sowing of green manure (after plowing and a good aging of the ground), may be carried out with centrifugal fertilizer spreader to the use of which is made to follow the passage a chain harrow to allow a minimum burying the seed distributed.
For fertilization using: centrifugal spreaders, compost spreaders, manure spreaders.
- Preparation of the seedbed: this operation generally consists of an aging and leveling the ground next to the primary processing (plowing). This step can be implemented either with harrows to fixed working parts (harrow teeth by providing two or more steps depending on the Clod soil) that with harrows to working parts driven by the PTO (power harrow), remains a recommended final step always with a rotary harrow. This operation can also be performed with milling machines that if on the one hand allow to obtain an excellent level of refining, on the other hand determine the disintegration of the ground and the sole working with the now well-known negative effects.
For the reasons mentioned above we recommend use as few as possible of the drills. It follows that it would be preferable to the adoption of equipment such as harrows, consistent with the needs of both agronomic and economic of the business.
Using: grubber (farmer), combined cultivator, harrows, hoes (or milling) rotary rollers.
- Transplantation: is an operation that is well suited to be mechanized by:
Mechanical transplanter which is a machine for the planting of plants or parts of them. It consists of a frame, usually worn or semi-mounted, on which there are accommodated a power supply device, a distribution device, the organs coulters for the opening of the groove of pose, the organ ridger that blocks the seedling and closes the furrow; organs for the compaction of the soil around the roots of the seedling and the subsequent closure of the same, other organs for complete coverage and regulation organs and those for attachment to the tractor.
Facilitator transplanter: constituted as the mechanical transplanter, is only devoid of the feeding device because this function is performed manually by one or more operators located on board the machine itself.
Facilitator transplanter for nursery: operating machine for the planting of seedlings. Constituted by a furrow opener, one or more stations for the operator in charge of the seedlings and transplant organs for the covering of the map.
In Figure 24 are reported some essential parts of a machine for transplanting seedlings of strawberry.
Figure 24 - Essential images for understanding the mechanical transplanting strawberry seedlings.
- Interventions post-emergency: weed control on soil mulched (then in the passing lanes between mulches), is generally mild, if it is necessary can be done either manually (weeding) and with the aid of brushcutters flush. Essential is the time distribution of straw between the mulches in pre-harvest, thus it avoids the contamination of the fruits by splashes of mud in case of rain and at the same time takes place also a function of containment of the weeds . Using the hoe.
- Health measures: the adoption of appropriate crop rotation (possibly least four), an appropriate choice of variety, fertilization (substantial soil improver) balanced and careful soil management (avoid water stagnation), allow to greatly limit the interventions pest. The treatments are carried out using boom sprayers (jet brought), is vital verification (annual calibration) operation of sprayers to avoid to have uncovered parts of the vegetation and useless waste product into the environment.
Are used: the sprayer bar and pneumatic systems for the harvest of insects. The first (Figure 25) is the equipment most used for the distribution of liquid to crops weeds of full field. There are a wide range of models carried, towed or self-propelled with spraying based on mechanical pulverization of the jet (nozzle traditional) pneumatic or centrifugal (less common). In recent years the most innovative machines were introduced electronic systems for the ongoing monitoring of the dose applied and a series of technical features aimed at improving the safety of use. They are useful systems for the reduction of the drift which the aeroassistenza or the use of anti-drift nozzles (air-induction).
Figura 25 - Equipment for sprayer bar.
About pneumatic systems for the capture of insects, it is a physical method for the control of insects based on the use of vacuum machines of various shapes and sizes and the use of which is currently very limited. The working times are highly variable depending on the model (from 0.42 to 6.67 hours/ha) and therefore the technique is very often not convenient from an economic standpoint. (Figure 26)
Figura 26 - Automatic vacuum for the capture of insect.
This technique, still to be concluded from the mechanical point of view (especially in terms of speed of the air suction, adaptation to crops and systems of trapping of insects), has the obvious advantage such as no use of product exogenous such as insecticide and other chemicals. However there are some drawbacks such as:
- no selectivity as either capture all insects present, including the beneficial insects such as natural enemies and parasite pests;
- necessity of repeated passages (if it is the sole means of controlling employee) with the consequent possibility of soil compaction;
- possible negative effect on the spread of viruses or fungus.
Diseases caused by fungi
Black Root Rot: the disease causes poor yields and serious plant losses, with infected plants failing to produce new roots. Roots of severely infected plants turn black and rot (Figure 27). It is a disease at load of the root and of the collar of the plant that, in local circumstances, affect the plants more frequently than the classic diseases linked to the action of individual soil-borne fungi, such as Verticillium spp., Phytophtothora spp. Pythium spp., Rhizoctonia spp., Fusarium spp. The described syndrome cause a gradual decay of the plants and it is attributed to simultaneous action of a pool of fungal pathogens including, in addition to those already mentioned, Ramularia spp. and Rhizoctonia fragarie .
Therefore, the cause of the disease is complex, with several pathogenic fungi being implicated along with certain environmental stresses, such as cold injury, excessive water near roots and soil compaction. In some cases, the disease has been associated with interaction between lesion nematode and particular soil borne fungi.
Figure 27 - Necrotic roots as a result of progressive degeneration of the plant to multiple attack of various pathogens, including the principal, the Rhizoctonia fragariae , which led accumulate, the "soil sickness". On the right, the final stage of the disease symptoms on the plant.
The affected plants, with temperature increasing, slow they vegetative activity, appear stunted and small size. With the progression of the disease occur reddening of leaf margin, progressive desiccation of vegetation starting from the outer leaves, up to the complete wilting of the plant. The cause of the disease spread in local strawberry field is probably related to decrease of the crop rotation, due to the adoption of new fixed protection structures. This leads to more frequent return of the crop on the same soil, on which they are grown intensively other crops that are home to some of the pathogens responsible of the disease, increasing the inoculum of these fungi on the soil devoted to strawberry.
The disease control can be achieved through chemical disinfection of the soil by fumigant action made products. This practice, however, is severely limited by applicable law and when you adopt integrated pest management strategies that favor the use of defense agronomic criteria (large rotations, addition of organic matter) or physical (soil solarization). Interesting also seems the use of green manure species having fumigant effect or the use of products derived from the dehydration of the same "biocides" species, distributed on the soil in pellets.
Leaf spot: it is one of the most common and widespread diseases of strawberry. The causal agent is Mycosphaerella fragariae (Tul.) Lindau, 1897; anamorph: Ramularia brunnea Peck. The synonyms of the anamorph are: Ramularia tulasnei Sacc. 1886; Ramularia grevilleana (Tul.) Jorst., 1945; Cylindrosporium grevilleanum Tulasnei. Remember that the teleomorph is the sexual reproductive stage, typically a fruiting body; the anamorph is an asexual reproductive stage, often mold-like. The holomorfo the whole fungus, including anamorph and teleomorph is, therefore, the whole metagenesis of the fungus. The taxonomy of Mycosphaerella fragariae, is the following: Domain: Eukaryota (Chatton, 1925) Whittaker & Margulis, 1978; Kingdom: Fungi (L., 1753) R.T. Moore, 1980; Subkingdom: Dikarya D.S. Hibbett et al., in D.S. Hibbett et al., 2007; Division: Ascomycota (Berk. 1857) Cavalier-Smith 1998; Subdivision: Pezizomycotina O.E. Eriksson & K. Winka, 1997; Class: Dothideomycetes O.E. Eriksson & K. Winka, 1997; Order: Mycosphaerellales (Nannf.) P.F. Cannon, 2001; Family: Mycosphaerellaceae Lindau, 1897; Genus: Mycosphaerella Johanson, 1884. The teleomorph synonyms Mycosphaerella fragariae are: Cylindrosporium grevilleanum Tul.; Sphaerella fragariae (Tul. & C. Tul.) Sacc., (1882); Sphaeria fragariae Tul., (1856); Stigmatea fragariae Tul. & C. Tul., (1863).
Mycosphaerella fragariae is also the cause of black seed disease of strawberry fruit, which occurs occasionally in North America where Mycosphaerella leaf spot is present. Prior to the development of resistant cultivars and improved control programs, leaf spot was the most economically important strawberry disease.
Leaf symptoms vary with strawberry cultivar, strain of the fungus causing disease, and environmental conditions. Leaf lesions or "spots" are small and round (3-8 mm diameter),
dark purple to reddish in color, and are found on the upper leaf surfaces. The center of the spots becomes tan to gray to almost white over time, while the broad margins remain dark
purple (figure 28). Lesion centers on younger leaves stay light brown, with a definite reddish purple to rusty brown margin. Numerous spots may coalesce and cause death of the leaf. Large,
spreading lesions that involve large portions of the leaflet are formed on some highly susceptible cultivars; the centers of which remain light brown. In warm humid weather, atypical
solid rusty brown lesions without purple borders or light colored centers may form on young leaves. Lesions are evident on the undersurface of the leaf but are less intense in color,
appearing as indistinct tan or bluish areas (figure 28).
Figure 28 The Leaf spot of strawberry caused by Mycosphaerella fragariae , anamorph Ramularia brunnea . It appeares with small red spots on the leaves, with purple edges and white center. the infection is rare in strawberry field of first year.
Leaf stems (petioles), runners, fruit stalks (pedicels), berry caps (calyxes) symptoms are almost identical to those on leaves, except for fruit. Only young tender plant parts are
infected by this pathogen.
Fruit symptoms are superficial black spots (6 mm in diameter) form on ripe berries under moist conditions.
These spots surround groups of seeds (achenes) on the fruit surface. The surrounding tissue becomes brownish black, hard and leathery. The pulp beneath the infected area also becomes
discolored, however, no general decay of the infected berry occurs. Usually only 1-2 spots occur on a berry but some may have as many as 8-10 "black-seed". Symptoms are most
conspicuous on white, unripe fruit and on ripe fruit of light colored cultivars. Economic losses in this case are due to unattractiveness of "black seed" spots on fruit, rather than fruit rot.
Signs (visible presence of the pathogen). Later in the season, dark specks (sclerotia and/or perithecia) may be seen in older lesions.
Regarding to disease cycle, in the south regions, perithecia and sclerotia are absent. Spores (conidia), are produced in small dark fruiting bodies (pseudothecia) within leaf lesions, and serve as
inoculum. In this instance infection is a continuous process with older lesions producing conidia to infect young leaves during each season. Conidia landing on leaf surfaces produce
germ tubes which penetrate through natural leaf openings (stomata) on upper and lower surfaces of leaves. New conidia are produced on clusters (fascicles) of conidiophores which
grow out through stomata. These are carried to new leaves by rain splash, and the disease cycle begins again.
In northern growing regions, the life cycle is somewhat different. Three sources of primary inoculum may be present: conidia overwintering on living leaves, conidia from overwintering
sclerotia, and ascospores. Abundant conidia, produced in early summer on lesions on both upper and lower leaf surfaces and lesions on other plant parts, are spread primarily by water
splash. High rainfall can lead to disease of epidemic proportions. Sclerotia are produced profusely on during the winter on dead infected leaves. These may also produce abundant
conidia in the spring. Conidia also develop on occasion from the bases (apices) of perithecia.
Perithecia are produced primarily on upper surfaces of overwintered leaves. Forcibly discharged ascospores. from these perithecia are wind disseminated. It is not known if these
serve as an important source of primary inoculum, but they are most probably a means by which genetically different strains of the fungus may travel long distances. Mycosphaerella fragariae establishes in the stigma at the time of flowering and then grows to the achene. From there it infects surrounding berry (receptacle) tissue. Conidia produced in leaf infections are probably the primary inoculum source for fruit infections.
The conditions favoring infection regards same conditions. Leaf spot may reach economic threshold levels, provided young leaves and inoculum are present, under conditions of high temperature and long period of leaf wetness. Research results show most severe infection of young leaves to occur during periods
of leaf wetness from 12 to 96 hours, when temperatures fall in the range of 15-20 °C. This data suggests fungicide treatments should be applied in early spring, and after renovation of
plantings if inoculum was present.
regarding disease management, the plant in light, well drained soil with good air circulation and exposure.
Choose disease resistant cultivars suitable for your location. Plant only disease free plants purchased from reliable nurseries. Apply nitrogen fertilizers only at renovation to reduce succulent new leaf tissue which is more susceptible. Carefully space runner plants in matted-row culture and control weeds in all plantings to improve air circulation and reduce drying time for leaves. Remove older or infected leaves before setting runners in new plantings. Removing and burning all debris at renovation (after harvest) helps to reduce overwintering inoculum of leaf pathogens. If leaf diseases are a problem in the planting, follow a fungicide spray schedule recommended for control of leaf
diseases and fruit rots to aid in control. Thoroughly cover all above ground plant parts with spray, especially undersides of leaves. For more information on fungicide programs see "Pest
Management Guidelines for Commercial Small Fruit Production" . Check product labels for timing and rates of application for products.
Leaf blotch and Stem-End Rot: Gnomonia leaf blotch occurs sporadically in annual strawberry production systems and is often associated with plant source. The pathogen is most commonly found on foliage in our region, on rare occasions it may infect flower parts and can cause stem end fruit lesions. It can build up in plug production facilities causing leaf blotches detracting from the look of the plug plants. However, the pathogen rarely causes economic damage.
Gnomonia infects leaves causing brownish to purplish lesions that begin small but expand to large areas, especially as lesions coalesce to form large blotchy areas of damage on leaves (Figure SS-1). Lesions can have various shades and are visible on the upper and lower side of the leaf (Figure SS-2). These spots often occur on the end of a leaflet and are V-shaped. As the disease progresses, the outer leaves of affected strawberry plants often die. Frequently, the lesions have small raised bumps, or pycnidia, visible with a 20 to 30x hand lens. If these bumps are not visible in the field, they emerge after a short time in incubation chambers (Figure SS-3). The pycnidia are have a yellow to brown color, ostioles (holes on top) and exude small conidia that have two oil bodies, one at each end of the conidia (Figure SS-3). The pathogen can also form sexual structures visible as black long necked and flasked shaped structures called perithecia often visible on leaf spots and petiole lesions. Under favorable weather conditions, the pathogen causes a flower blast where flowers are heavily colonized by the pathogen turning the calyx, peduncle and other flower parts brown. In some cases, the pathogen colonizes the stem of the fruit causing stem-end rot (Figure SS-4) characterized by circular to irregularly shaped brown lesions. Fruit may be infected at all stages of development.
The biology and ecology of the pathogen in NC and surrounding area is not well documented. Gnomonia comari sensu lato affects numerous herbaceous Rosaceae genera including Fragaria, Comarum, Geum, Potentilla, Alchemilla, Agrimonia, Sanguisorba and also Epilobium hirsutum in the evening primrose family. However, in the majority of cases, the initial inoculum is introduced into plug facilities and fruiting fields with transplants. Lesions on these plants produce pycnidia that ooze conidia that are then splash dispersed. The conidia enter the plant through stomata or wounds.
In most cases specific management recommendations are not needed since the disease rarely develops to a point where economic losses occur. However, lesions on leaves, the blotches, can develop to concerning levels on plugs and soon after transplanting in fruiting fields. These leaves may affect early plant establishment but new leaves develop quickly and the disease does not persist into the early spring or fruiting period. In one year of 20, persistent cool wet weather during flowering and early fruit development led to flower blast and fruit stem-end rot that impacted yield in some fields. Little data is available for this disease but products effective against Phomopsis leaf blight appear effective against this disease. Products, rates and timing are highlighted in our strawberry IPM guide
Gnomonia comari is a fungal plant pathogen that causes a minor disease of strawberry. To reproduce, Gnomonia comari forms globose and beaked perithecia. The base of the perithecium (250-600 µm in diameter) is buried in the host tissue and the cylindrical neck (200-1200 µm long) protrudes from it. Many asci (20-35 x 3.5-8 µm) are produced within the perithecium and each ascus contains 8 ascospores. Mature ascospores (6.5-13 x 1.5-2.5 µm) are hyaline, straight or slightly curved and submedially septate. Ascospores of G. comari also contain conspicuous oil droplets and lack appendages (CABI, 2008; Maas, 1998).
The anamorph of Gnomonia comari, Zythia fragariae produces pycnidia that are yellowish brown, soft walled, and ostiolate with no conspicuous neck. The conidia (5-6 x 2 µm) are hyaline, contain two oil droplets, have rounded ends, and are borne on short unbranched conidiophores.
Symptoms of leaf blotch could be confused with those of Verticillium wilt, as both diseases affect outer leaves of the strawberry plant. Foliar symptoms of Gnomonia comari also may be similar to the light brown necrotic spots caused by Phomopsis obscurans. While Gnomonia comari can be distinguished from Verticillium species by the presence of beaked perithecia or pycnidia in leaf lesions and spores with discrete oil droplets, differentiating between Gnomonia and Phomopsis is more difficult. The fruiting structures and spores of Gnomonia comari and Phomopsis obscurans can look similar although Gnomonia pycnidia tend to be yellow to brown and Phomopsis pycnidia tend toward black; Phomopsis conidia do not have the prominent oil bodies. It is important to note that Gnomonia comari produces both perithecia, bearing asci with ascospores, and pycnidia from which conidia are borne while Phomopsis obscurans is an asexual fungus. and can only produce pycnidia.
When signs of the pathogen are absent, incubating symptomatic leaves or leaflets for 24 to 48 hours in a moist chamber usually results in abundant sporulation of the fungus.
Figure 29 - Gnomonia Leaf blotch and Stem-End Rot of Strawberry caused from Gnomonia comari, teleomorph, Zythia fragariae, anamorph. Gnomonia leaf blotch on strawberry leaf. Several lesions may coalesce to cause large blotches on leaves. Note small raised bumps (pycnidia) surrounding the lesions. Gnomonia leaf blotch showing a range of symptoms on the lower and upper surface of the leaves. (top left). Gnomonia stem-end rot showing the brown circular to irregular lesions that form at the stem end of the fruit (in upper right). Pycnidia erupting from stem lesions, ~50x (below left). Pycnidia erupting from peduncle lesions, ~20x (above center). Small conidia (5-6 x 2 µm) with 2 oil bodies that refract light (bottom right).
Gray mold: the causal agent is Botritis cinerea Pers., 1822, anamorph, Botryotinia fuckeliana (de Bary) Whetzel, 1945, teleomorph. The fungus is usually referred to by its anamorph (asexual form) name, because the sexual phase is rarely observed. The teleomorph (sexual form) is an ascomycete, Botryotinia fuckeliana, also known as Botryotinia cinerea. The taxonomy of this fungus is the follow: Superkingdom or Domain Eukaryota Chatton, 1925; Kingdom: Fungi .L. Jahn & F.F. Jahn, 1949 ex R.T. Moore, 1980; Division: Ascomycota Bold, 1957 ex T. Cavalier-Smith, 1998; Subdivision: Pezizomycotina O.E. Eriksson & K. Winka, 1997; Class: Leotiomycetes O.E. Eriksson & K. Winka, 1997; Order: Helotiales Nannf., 1932; Family: Sclerotiniaceae Whetzel ex Whetzel, 1945; Genus: Botrytis P. Micheli ex Pers., 1794.
Particularly serious disease in strawberry plants under small tunnel, in case of springly trends humid and rainy but can also cause extensive damage to the productions in protected cultivation. The disease is particularly evident when it affects the fruits, causing brown spots and translucent (Figure 30) that hold the typical mold of gray. The fungus, however, is also developed to occur in other plant organs such as leaves stalks, sepals, flowers, leaves, causing damage sometimes even more serious than those on the fruits.
The strawberry fields particularly dense, the excess nitrogen fertilizers, the use of varieties vigorous, poor cleaning Fragoleto, stagnation of humidity due to poor turnover of air favour the development of the disease and make it more complex and expensive the control of the disease.
Figure 30 - Gray mold of fruits rot may start on any portion of the fruit but is most frequently initiated under the calyx and spread when fruit touch other rotten fruits or when spores are water-splashed to other blossoms or fruits. Affected tissue turns brown and becomes soft and watery. Diseased portions are usually covered with gray velvety growth (centre) or white mycelia which are covered with spores (right).
In crops under greenhouse and large tunnel is necessary to cure the aeration, practice that reduces the need in each case the frequency of control interventions, which generally make the essential assets and on crops when the course winter and spring is particularly wet and rainy. Regarding the small tunnel, in addition to the care of the air exchange, it is often necessary, especially in wet springs, perform preventive treatments with registered products, respecting the times of security. So, for the disease control, we resort to the use of fungicides, but you can also carry the fight to the agents that cause dents, cracks or sores in the fruits. The pathogen fits with great ease to fungicides and, therefore, controlling microbiological becomes much less costly and more effective. In this regard it may be recalled that Clonostachys rosy f.sp. rosy (Link) Schroers, (1999) is a parasitic fungus of Botrytis cinerea. This parasitic fungus is able to suppress the production of spores of the pathogen and with its hyphae wraps those of the pathogen, penetrating and growing inside of conidia and hyphae of Botrytis cinerea. Clonostachys rosy f.sp. rosy belongs to the Ascomycota, Sordariomycetes, Hypocreomycetidae, Hypocreales, Bionectriaceae (Figure 31).
Figure 31 - Clonostachys rosea f.sp. rosea, a fungus of the chilean Patagonia, can be a great resource to the environment. It is an endophyte fungus that can successfully control the development and spread of gray mold of strawberry.
The conidia are hyaline (or nearly so), as are the tips of the conidiophores (Figure 32). The vegetative mycelium of the fungus is also colourless, appearing white to the naked eye in its "fluffy" stage. But mature fungal colonies are a dingy grey.
The colour is in the lower parts of the conidiophores, which are distinctly brown and thick-walled when seen under the microscope (Figure 32).
Figure 32 - Asexual fructification of the causal fungus agent of gray mold of strawberry fruits. It is represented by characteristic conidiophores typical of Botrytis cinerea. Under the high power of the microscope, the fungus looks like bunches of grapes. Large numbers of rounded conidia are budded off at the branched ends of the long (to 2 mm), stiffly upright conidiophores.
The fungus also produces, in older cultures, the sclerotia that uses very durable as defense structures; the same spends the winter as sclerotia or mycelium as real; in both cases in the spring germinates and produces conidiophores.
The conidia are dispersed by wind and rain water and cause new infections.
This species has been observed a significant genetic variability in terms of polyploidy. In addition, the sexual phase (Botryotinia fuckeliana) has been observed in very rare cases.
Powdery mildew: powdery mildew of strawberry is caused by the obligate parasite.
Podosphaera aphanis (Wallr.) U. Braun et S. Takam., 2000, which affects leaves flowers and fruits of strawberry worldwide. Podosphaera aphanis formerly known as Sphaerotheca macularisfragariae (Harz) Jacz, 1927.
The taxonomy of Podosphaera aphanis is as follows: Domain: Eukaryota Chatton, 1925; Unikonta; Opisthokonta Cavalier-Smith, 1987; Holomycota; Kingdom: Fungi T.L. Jahn & F.F. Jahn, 1949 ex R.T. Moore, 1980; Subkingdom: Dikarya D.S. Hibbett et al., in D.S. Hibbett et al., 2007; Phylum: Ascomycota H.C. Bold, 1957 ex T. Cavalier-Smith, 1998; Subphylum: Pezizomycotina O.E. Eriksson & K. Winka, 1997; Class: Leotiomycetes O.E. Eriksson & K. Winka, 1997; Order: Erysiphales H. Gwynne-Vaughan, 1922; Family: Erysiphaceae Tul. & C. Tul., 1861; Genus: Podosphaera Kunze,1823; Species: Podosphaera aphanis (Wallr.) U. Braun et S. Takam., 2000.
Systematic of powdery mildew causal agents sharply changed during the last years . The taxonomy of Erysiphales recently was revised basing on DNA sequence data. Identification pathogens from Erysiphales now require morphology peculiarities of teleomorph and anamorph, incorporates characteristics to the whole.
The anamorph of Podosphaera aphanis is Oidium ruborum Rabenh., 1878, synonymus Oidium fragariae Harz, 1887.
Podosphaera aphanis is a fungus ectoparasite obliged and specialized, which then requires the strawberry plant to survive. Powdery mildew of strawberry must overwinter as mycelium in the tissues of green plant (remaining quiescent especially in the buds or leaves that remain alive in the winter), or by the cleistothecia. The cleistothecia are the bodies containing asci, have round shaped whitish beginning and then dark brown, almost black when ripe completed (Figure 33).
Figure 33 - Cleistothecia of Podosphaera aphanis from which, with their maturity, the asci with ascospores escape. The cleistothecia are provided with fulcrums (filiform appendages which extend from the outer surface of the fruiting body) that, in this case, are typical of the genus Podosphaera.
Ascospores contained in the cleistothecia germinate, like conidia (asexual spores that are produced during the summer), producing a mycelium tube. It extends up to form a penetration stylet that, once contact the cell wall of the leaf, form a structure (haustorium) to form enlarged and specialized to absorb water, minerals and nutrients from the cell, without directly causing the death. The fungus produces on the surface of a dense mycelium (powdery white mold) which in turn produces new haustoria. The pathogen can affect leaves, stems, stolons, flowers and fruits. On leaves the early infections are characterized by small white areas, dusty-looking, that grow normally on the undersides. Later, if the plant is not treated with fungicides, the spots enlarge and also appear on the upper surface, up to cover the entire leaf blade of a white powder (Figure 34).
Figure 34 - Initial spots of mildew on the upper surface of the leaf.
The disease is a major pest problems in protected cultivation, especially in conditions of poor aeration. It affects all organs epigeal plant, which can be of a whitish mold. Then the affected leaves have the leaf margins typically curved upwards and, in case of pressure of the particular disease or varieties not very sensitive, showing the red areas that may necrose, affecting much of the leaf (Figure 35).
The fungus can cause abortion or malformation of the flowers, while on the fruit produces a mycelium sparse and widespread. The seeds tend to protrude abnormally and the fruit is hit softer, less intense color, it retains less of healthy fruit and tends to rot.
Strong attacks the foliage can lead to necrosis and defoliation. Production losses are therefore due to infection to flowers and fruits.
Figure 35 - White mycelium spread on fruit (left). Fruits softer, less intense color, from which the seeds tend to protrude abnormally (right).
The fungal pathogen causes severe losses in traditional strawberry cropping systems in Mediterranean climates and in greenhouse soil-free systems, which are more common in central Europe and in some areas of Northern Italy. Leaf infections reduce photosynthesis, cause necrosis or even defoliation and, consequently decrease fruit yield. Mild infection on fruit causes slight discoloration and shortened shelf life, while more severe infection causes deformation and cracking in fruit. Crops grown in warm, dry Mediterranean climates are particularly vulnerable.
Growing strawberries in raised beds under high tunnels or in greenhouses can positively affect fruit quality and shelf life. These systems also allow growers to schedule their harvests to coincide with periods of market demand.
Mildew of strawberries is a widespread disease over the world. Powdery mildew of strawberries was noted only in glasshouses. There are some possible reasons for emergence of powdery mildew: new varieties and climatic changes. Milder winters might allow overwintering of Podosphaera spp. and hot summers increase rate of disease progress.
The disease damages all aerial plant tissues, including fruits.
The method also helps to control several important diseases like grey mould, fruit rots and root rots. However, without the inhibitory effect of rain on conidia germination, sheltered crops tend to have more powdery mildew infection. Long periods at around 20°C and the high relative humidity in tunnels provide favourable conditions for Podosphaera aphanis. These infections can appear early and develop quickly, especially on sensitive cultivars, like Elsanta and Tamar, the
most common strawberry varieties in the two studied environments.
Controlling strawberry powdery mildew in the typical production system of northern Italy, soil-less production in tunnels, generally requires at least seven or eight fungicide treatments per growing. Crops grown in the open may require 12 to 16 sprayings per season. Regular, intensive fungicide applications contrast with the goals of integrated pest management, so a decision support system (DSS) for applying pesticides only when strictly needed is desirable. Development and maintenance of a DSS is costly, therefore, any new DSS should be designed to be valid over a large area. As strawberry is a relatively minor crop, a DSS should cover several production areas which have similar problems in order to maximize its economic value.
Although information is available on the efficacies of pesticides and biocontrol agents against Podosphaera aphanis under field conditions, it is not known if strawberry powdery mildew
populations, adapted to different environmental conditions, differ in sensitivity to particular fungicides. Different sensitivities have been documented for subpopulations of Phytophthora infestans and Uncinula necator, suggesting that disease models and control strategies should be adapted to particular geographical regions. Even if different pathogen populations are consistently sensitive to sulphur treatments (the oldest fungicide applied against powdery mildews), different pathogen populations may differ in their sensitivities to new fungicides or biocontrol agents.
Active ingredients based on triazole chemistry, like penconazole or miclobutanil, strobilurines (e.g. azoxystrobin or kresoxym-methyl), or pyrimidines (fenarimol) are expected to provide consistently effective disease control. However, local differences may exist, reflecting differences in usage
patterns, genetic differences among pathogen subpopulations or interactions between the compounds and the local climactic conditions. Among low impact control agents used against powdery mildews, mineral salts, such as monobasic potassium phosphate, plant extracts, resistance inducers such as benzothiadiazole, and microbial antagonists, such as Ampelomyces
quisqualis, Bacillus subtilis and Trichoderma, have been tested or developed as commercial products for control of powdery mildews on other crops. However, little is known of their efficacies against strawberry powdery mildew. There are no reports on genotypic variability and sensitivity to fungicides among populations.
It is necessary to prevent the development mildew instead of waiting the first infection. From the moment you make the coverage with the tunnel is necessary to pay more attention to the disease. The periods at higher risk are for summer, when the relative humidity is high. The plants must be protected with fungicides, paying more attention when they are in the early stages of development. The previous phase flowering, when you have a strong production of new leaves, is the most delicate defense antioidica. An imbalance of nitrogen than phosphorus and potassium can cause a greater sensitivity to powdery mildew in plants, as it promotes the lussureggiamento foliar and delays the maturation of tissues. It is good to avoid infections stolons or delete them, because they are more susceptible to the disease and act as a "reservoir" of inoculum. You should also remove the plants at the end of the cycle or treat even after harvest to avoid the presence of inoculum that can continue to spread. Because cleistothecia seem to be one of the most important sources for inoculation spring, you need to verify their presence on the seedlings before wintering, maintaining high, in their presence, the focus in the early stages of cultivation.
To optimize the use of fungicides, it is important to apply them in the moment in which they can exert the maximum effectiveness against the pathogen. The development and virulence mildew depend not only on the presence of inoculum, by varietal susceptibility and environmental conditions. Previous studies show that the temperature and the humidity are the key factors in determining the development of the disease. Estimate when the pathogen is active in the crop will reduce the use of pesticides.
Considering the prospects for development of new defense strategies, it is important to understand if they are sustainable. Researcher's attention is often paid to the assessment of their effectiveness in protecting against disease and the study of the mechanism of action of the agents involved. A crucial aspect, however, that is often overlooked in the research phase of new strategies, is the assessment of the sustainability of their potential introduction of a system of integrated protection and the possible socio-economic constraints related to the stage of application in agriculture.
Sustainability has three dimensions: economic, environmental and social.
For environmentally friendly agriculture is necessary to identify and use techniques with lower environmental impact that they are able to ensure the maintenance over time of the production capacity of an agro-ecosystem despite the exploitation to which it is subjected, and at the same time are compatible with the objectives economic efficiency and management of the company.
- The economic dimension of the fitness to maintain a production capacity can meet the needs of current and future, through the efficient use of natural resources.
- The environmental dimension relates to the ability to maintain the natural resources in sufficient quantities, reducing damage and also to make the benefits generated by agricultural activity on the surrounding environment.
- The social dimension refers to the attitude to maintain an equity capital, the ability to adequately support the producers by the community social institutions and the ability to reduce the risk to human health of consumers, farmers and residents in agricultural areas.
To measure the economic viability of a defense strategy must estimate the final results, evaluating the costs and benefits obtained from the use of the strategy to be analyzed with those that could be achieved with another method of defense, reducing them in the same structure evaluation. This estimate is the first step and the most important because the economic, ecological and social benefits provided by the defense strategy, can be demonstrated and publicized and the data obtained can justify economic investment made by the farmer and lead to new funding so they can support new projects and research.
In conclusion, in practice, the struggle, in good times, must be preventive. You can use the active principles recorded on the crop, in activities cytotropic or systemic, to be accompanied also with interventions based wettable sulphur, in the formulations more micronized, as a product of contact.
Leather Rot: the causal agent is Phytophthora cactorum (Lebert & Cohn) J. Schröt., 1886, a fungus whose taxonomic following: Unikonta; Opisthokonta Cavalier-Smith, 1987; Holomycota; Kingdom: Fungi T.L. Jahn & F.F. Jahn, 1949 ex R.T. Moore, 1980; Subkingdom: Dikarya D.S. Hibbett et al., in D.S. Hibbett et al., 2007; Phylum: Oomycota Winter, 1897; Class Oomycetes Winter, in Rabenhorst, 1879; Order Pythiales; Family Pythiaceae; Genus Phytophthora Heinrich Anton de Bary, 1875.
Figure 36 - Microscopic distinctive characteristics of Phytophthora cactorum: sporangia, typically 30 μm long (+/- 5 μm) and 26 μm (+/- 4 μm) wide, are broadly ovoid, distinctively papillate, and are usually borne terminally (a); acropetal sporangia carried by a long sporangioforo (b) Oogonium with paragynous antheridia close to oogonial stalk (Oospores are slightly aplerotic) (c); chlamydospore (have moderately thick cell walls of 1-1.5 μm and diameter range from 25-40 μm, usually at the tip of generative hyphae but occasionally via intercalary formation (d). Symptoms on fruits: strawberry leather rot on vegetation and fruits (e); leather rot with white sporulation (e).
Diagnosis of leather rot caused by Phytophthora cactorum is based on morphology of the pathogen or through the use of molecular techniques. Identification is based on characteristics of the mycelium, shape of zoosporangia (asexual reproductive structures) and the presence and shape of oospores (sexual reproductive structures).
If zoosporangia are present, and are roughly lemon-shaped with a short pedicel (stalk at the base of the spore) after the zoosporangium has been detached and contains a papilla (small swelling on the tip of the spore, see arrow in Figure 7), one can be fairly confident it is a member of the Phytophthora genus.
In most cases, identifying the pathogen to genus will provide enough information to identify proper prevention and control strategies.
Phytophthora cactorum is considered water molds and require water to spread the spores and to germinate on new hosts. The spores can easily spread in irrigation water and can splash from one plant to another during watering. In addition, zoospores, which are motile, are normally considered the infective spore and can move readily when free water is available. Therefore, it is crucial to remove infected plants immediately to prevent further spread, reduce periods of prolonged wetness, and provide adequate ventilation.
Fungicides should be considered as a tool for managing Phytophthora and if not used properly (according to the manufacturer's label) they will not be effective or may cause more harm than benefit. However, they are your primary defense in an existing crop and provide at least some level of management when used appropriately. Getting Phytophthora under control requires a longer-term strategy and actions that focus on changing and improving procedures and materials to reduce the opportunity for spread or reintroduction of the pathogen. Successful management of Phytophthora in a nursery has been accomplished in the past when dramatic measures were undertaken. Some growers keep a clean laboratory or surgical room in mind as they think through their nursery sanitation procedures.
Preventative applications of foestyl-AL, potassium phosphite, propamocarb hydrochloride, trifloxystrobin, Bacillus subtilis, dimethomorph, mefenoxam, etridiazole may aid in reducing disease spread, but only complete control can be achieved if the infected planting material is destroyed.
Use only unopened bagged growing media stored on a covered paved surface that can be periodically washed down with a 1:3 ratio of bleach (sodium hypochlorite) to water. It is likely that the pathogen will move into your growing media if not bagged or completely covered.
Each use, use only disinfected tools and hands (disposable latex gloves that can be purchased at the grocery store or professional cook equipment stores work well). Bleach works by oxidizing or destroying the molecular bonds in microorganisms. Store purchased bleach solutions are now usually 6% sodium hypochlorite. The older non-concentrated versions are probably around 5% solutions. Avoid mixing bleach with acids or toxic chlorine gas may result. Always use with good ventilation.
Store new pots in sanitized areas similar to the growing media storage area. Your best option is to always use new potting containers, but if this is not feasible submerge potting containers in a 1:3 ratio of bleach (sodium hypochlorite) to water with agitation for a minimum of 10 minutes.
Make sure that bench surfaces are at high enough above the soil surface to avoid splashing from the ground below.
Sanitize all bench surfaces and tools used to prune or work with plants before each use. Remove or sanitize any surfaces that may drip water onto crop. Bleach dunking will cause steel to rust. Some growers handle this by dipping in bleach and then dunking in oil after drying.
Examples of disinfectants for tools and benches include: 1) 25% chlorine bleach (3 parts water and 1 part bleach; 2) 25% pine oil cleaner (3 parts water and 1 part pine oil); 3) 50% rubbing alcohol (70% isopropyl; equal parts alcohol and water); 4) 50% denatured ethanol (95%; equal parts alcohol and water); 5) 5% quaternary ammonium salts. Soak tools for 10 minutes and rinse in clean water.
Do not mix quaternary ammonia with bleach. The wood portions of your bench may be very difficult to sanitize because they are porous. Scrubbing to remove algae, scum, mildew and dirt before treating may help.
Well and not surface water should be used unless disinfected.
If hand watering is utilized, be sure to sanitize the hose and water wands with bleach solution and hang in areas where the ends of the hose or wands will not contact soil of other potentially contaminated surfaces.
Any new plants brought into the nursery should be kept isolated (including tools and continuous bench space used for these new plants) from other plants for at least 6 weeks to observe any disease or pest symptoms, and to avoid contamination with other crops.
Do not forget about other potential contamination surfaces like plant transport trailer or cart surfaces.
The identification of this disease is done by making the following observations:
1) Infects strawberry bloom and green or mature fruit.
2) Occurs where berries are exposed to soil.
3) Infected blossom clusters turn brown and die.
4) Green fruit become hard and leathery.
5) Lesions are not distinct but are usually somewhat soft and are sometimes dull pink to lavender or purple.
6) Ripe fruit develops a purplish colour and foul odour and taste; symptoms are most often noticed on ripening fruits.
7) Slicing infected berries will reveal darkened inner tissues.
8) White mould may grow from the diseased fruit.
Leather Rot often can be confused With anthracnose (Figure 37) and botrytis grey mould (Figure 30 and Figure 32).
Infection can take place anytime between bloom and harvest if spores are splashed or washed onto bloom or fruit. Leather rot is worse under cool, wet harvest conditions.
Scout in areas of the field where standing water or surface water run-off have occurred. Expect problems where straw is thin, blown away or washed away, exposing blossoms and fruit to the soil. Problems are most likely to develop after a heavy rain or irrigation.
Pick-your-own customers and workers are often the first to discover leather rot. Complaints of foul, sewage or chemical smells are common where leather rot occurs.
Anthracnose: produces wilting and plant death when it infects the crown. The causal agent is Colletotrichum acutatum a fungus whose taxonomic following: Domain: Eukaryota (Chatton, 1925) Whittaker & Margulis, 1978; Kingdom:: Fungi (L., 1753) R.T. Moore, 1980; Subkingdom: Dikarya D.S. Hibbett et al., in D.S. Hibbett et al., 2007; Division: Ascomycota (Berk. 1857) Cavalier-Smith 1998; Subdivision: Pezizomycotina O.E. Erikss. & Winka (1997); Class: Sordariomycetes; Order: Glomerellales Chadef. ex Réblová, W. Gams & Seifert (2011); Family: Glomerellaceae Locq. (1984); Genus: Colletotrichum Corda (1831); Species: Colletotrichum acutatum J.H. Simmonds (1968). The teleomorph of Colletotrichum acutatum is Glomerella acutata Guerber & J.C. Correll, (2001). Typical symptoms of Colletotrichum infection on stolons, petioles, and roots are presence of disk-shaped, dry, dark brown to black, sunken lesions that are sharply demarcated from the surrounding healthy tissues. When runners are girdled by lesions, the daughter plants beyond the lesion wilt and die. Lesions on petioles may also result in death of leaves. Infection of roots may result in stunting of plan (Figure 37).
Figure 37 - Colletotrichum acutatum induces symptoms on leaves (top left), producing stains reddish-brown, similar to burns, on the upper edge of the flap (above), or along the side margins (below); on these necrotic lesions, in high humidity conditions, can form masses of spores salmon color, whose microscopic examination allows identification of the fungus Colletotrichum acutatum, differentiating it from other pathogens. Symptoms on stolons (above, center) and on the petioles (top right, above and below) are represented by disk-shaped dark brown to black, with the margin marked clearly, surrounded by healthy tissue, which can result in death of the leaves. The fruits are susceptible to infection at all stages of development (in the center): immature fruit on the side or end, are observed notches brown, dry and hard that cause desiccation or mummification organ attacked; Typical symptom on ripe fruit are round, blackened, sunken, firm, and dry lesions which may be covered with salmon-colored spore masses. The photos below show the section lingitudinale the crown of the plants that appears to be reddish or brownish, until the cinnamon-colored, with different degrees of intensity (the first two photos below from left), the roots showing necrosis from brown to black, with net margin around and apparently healthy tissue (third photo) from which, in a humid chamber, can develop the conidia of the fungus (below), in masses of pink, purple or orange. These conidia are straight, cylindrical, fusiform, with a pointed end or attenuated of 8.5 to 16.5 x 2.4-4 μm, are produced in acervular conidiomata, or acervuli, and taken on conidiophores hyaline, setup, rights, rarely branched. The conidiogen cells are phialidic, hyaline, straight and cylindrical.
Various fungicides were assessed for their ability to control this disease, under laboratory, greenhouse and field conditions. The effective dose causing 50% inhibition of mycelial growth (ED50) was 0.5, 1, 1 and 2 ppm for the fungicides propiconazole, bitertanole, imazalil and hexaconazole, respectively. In the greenhouse, disease incidence, tested on three strawberry cultivars, showed that propiconazole treatment reduced mortality (3254%) but caused slight phytotoxicity in treated plants resulting in an abnormal plant growth. In field experiments over three years, dipping plants in aqueous fungicides suspension, carbendazim, bitertanole and thiabendazole, at transplanting reduced significantly disease incidence.
Other anthracnose pathogens were studed on strawberry: Colletotrichum fragariae and Colletotrichum gloeosporioides. Colletotrichum fragariae the original anthracnose fungus, was first identified in Florida in 1931. It spread throughout the southeastern United States and was responsible for crown rot and death of many plants in strawberry nurseries in the 1970s. It has a narrow host range, infecting only strawberry and a few weed hosts, and is rarely found outside the southeastern United States. Colletotrichum fragariae generally causes more severe petiole and crown symptoms than Colletotrichum acutatum, and Colletotrichum fragariae is considered by some to be a host-specific or con-specific form of Colletotrichum gloeosporioides.
In the late 1970s, Colletotrichum gloeosporioides was identified as the causal agent on plants obtained from Arkansas and North Carolina nurseries that died from a crown rot identical to that caused by Colletotrichum fragariae. It has a wide host and geographic range, causing diseases of many plant hosts worldwide.
Historically, Colletotrichum acutatum has been considered to be the anthracnose fruit-rotting pathogen, and Colletotrichum fragariae and Colletotrichum gloeosporioides have been associated with petiole and stolon lesions and crown rot; however, all three species may cause similar symptoms and may be found to occur on the same plant. Identification of these pathogens should be based on classical taxonomic characteristics or molecular techniques, not symptoms.
It was studied the infection process of strawberry petioles and stolons by Colletotrichum acutatum and Colletotrichum fragariae using light and electron microscopy. Both fungal species invaded the host tissue in a similar manner; however, Colletotrichum fragariae invaded the plants more rapidly than did Colletotrichum acutatum. Both species penetrated the cuticle via an appressorium, and their hyphae grew within the cuticle and cell walls of epidermal, subepidermal, and subtending cells. They began invasion with a brief biotrophic phase, in which they invaded living cells, before entering an extended necrotrophic phase, in which they proliferated among dead cells. Acervuli formed once the cortical tissue had been moderately disrupted and developed as a stroma just beneath the outer periclinal epidermal walls. Acervuli erupted through the cuticle and released conidia. Invasion of the vascular tissue typically occurred after acervuli matured but remained minimal.
The time from infection of the strawberry by Colletotrichum spp. to first sporulation (the latent period) is an important factor in the speed at which anthracnose may spread within a field. The latent period depends on the temperature and ranges from 23 d at 25 °C to 617 d at 5 °C. At 5 and 10 °C, the latent period was shorter for Colletotrichum acutatum than for Colletotrichum gloeosporioides and Colletotrichum fragariae; however, at higher temperatures the latent period for all species was similar. Appressoria and secondary conidia produced by Colletotrichum acutatum on symptomless foliage may be a significant source of inoculum for fruit infections and may also contribute to the availability of inoculum throughout the growing season. Conidial germination, appressorial production, and secondary conidiation are all favored by longer periods of wetness than the 4 h required for secondary conidia to form. Colletotrichum acutatum survived up to 8 weeks on leaves in greenhouse studies and up to 5 weeks on fabric. More conidia formed on leaves when exposed to flower extracts than when exposed to leaf extracts or water, suggesting that Colletotrichum acutatum inoculum levels on strawberry foliage may increase during flowering.
Rain splash is the primary means by which Colletotrichum spp. conidia are spread from plant to plant in the field. It was found that anthracnose fruit rot incidence generally declined as plant density increased and concluded that plant density reduced the amount of rain that penetrated the plant canopy, thus reducing the amount of splash. Most fruit infection occurred in a 25 cm radius of the source of the inoculum, an infected fruit. Splash dispersal of the conidia of the three Colletotrichum spp. was studied and found that conidia of Colletotrichum fragariae dispersed over the shortest distance and those of Colletotrichum acutatum dispersed over the longest distance. This was probably due to the greater amount of spores produced on infected fruit by Colletotrichum acutatum. Colletotrichum acutatum conidia may survive in soil and plant debris under dry conditions for up to 12 months, but conidia and sclerotia die rapidly under moist conditions, i.e., soil moisture ≥12%.
As our knowledge of the anthracnose pathogens and the epidemiology of anthracnose diseases has increased, so has our ability to control these diseases. Changes in cultural practices have resulted in reduced levels of disease. At the same time, development of more effective fungicides and their registration for use on strawberries have greatly reduced losses due to both anthracnose crown rot and fruit rot. Anthracnose-resistant cultivars also have reduced economic losses due to these diseases. Even so, growers may sustain severe losses when environmental factors are highly favorable for anthracnose development.
Root weevil: there are several species of root weevils which feed on strawberries. The most common are the strawberry root weevil (Otiorhynchus ovatus Linnaeus, 1758), in Figure 38 a, and black vine weevil (Otiorhynchus sulcatus Fabricius, 1775), in Figure 38 b. They are Coleoptera, Curculionidae. Larvae are found in the soil around the plant or imbedded in the crown (Figure 38, d). They are cream-coloured, or pinkish-white, legless, with c-shaped bodies and brown heads (Figure 38, f). Mature larvae range in size depending on species, for then becoming pupae in the soil (Figure 38, g). Adults are black or brown beetles with a characteristic long, probing mouthpart called a snout. They feed on strawberry leaves causing characteristic c-shaped notches on the leaf edge (Figure 38, e). The injury alone is not serious, but it indicates a potential problem with the larval feeding next year. Often the damages of this pests are confused with white grubs, winter injury and root or crown disease. Root weevils overwinter as larvae in soil. Larvae feed extensively on plant roots in spring. Adults begin to emerge from the soil during harvest. Adults are in the field throughout and early fall July and early August. Peak emergence and egg laying by adults occurs in late July through mid August. Root damage is not usually evident until the next spring. Although there is only one generation a year, populations can build rapidly within two years of planting. Scout fields in spring through bloom for areas of stunted growth. Carefully dig up the roots of a plant about 15 cm into the soil and look for grubs. If grubs are found, control measures should be taken after harvest when adults emerge. In mid to late summer look every 1-2 weeks for leaf notching caused by adult feeding. Black vine weevil adults can cause extensive and obvious damage to leaves, especially in young plants (Figure 38, h). However, not all species of root weevils cause noticeable notching.
Strawberry clipper weevil (Anthonomus signatus Say, 1831): it is a Coleoptera: Curculionidae which adults are 2-3 mm long, reddish-brown with a long snout (Figure 38, c). Strawberry clipper weevil adult is on bloom (Figure 38, i). The larvae and eggs develop inside strawberry buds and are rarely seen. Damage is caused by adult feeding and egg laying. Adults initially feed on pollen in strawberry buds and bloom, leaving round holes on buds and bloom as they do so When eggs are laid, the female weevil cuts the stem below the bud, which causes it to dry out and drop off (Figure 38, l and m).
It can be sometimes confused With strawberry root weevil. Adults become active in early spring, especially after a few warm nights. Damage occurs until all flower buds are open. Begin to monitor for clipper injury when strawberry buds emerge from the crown. Check older fields for first signs of damage. Check plants at the edge of the field near woods, bush and other overwintering sites. Examine buds and unopened blossom clusters for clipped buds. Sometimes the buds will remain partially attached, sometimes they will drop off the plant. Freshly clipped buds will be green and only partially shrivelled. As time passes these buds become quite dry and brittle. Assess damage by counting clipped buds in 0.2 m2 sections of the row. Continue twice weekly until petal fall.
Follow some management notes for strawberry clipper weevil, valid for all the pests. Apply an insecticide when the threshold is reached. Border sprays of the ten first rows may provide adequate control in newer plantings.
In most situations, only one corrective spray is required. Fields with severe strawberry clipper weevil pressure may require a second spray, if the action threshold is reached 7 days after the application of the first insecticide. Late strawberry clipper weevil damage is often prevented when tarnished plant bug sprays are applied.
Renovation should take place promptly after harvest.
Good weed control, especially the elimination of broadleaf weeds can reduce the survival of newly emerging strawberry clipper weevil adults.
In the final fruiting year, plough down the field immediately after the last picking. Follow this by summer fallowing and crop rotation, especially if you are replanting strawberries back into the same field.
Older fields tend to have more damage, so reduce pressure from clipper weevil by fruiting fields for two years or less.
Aphids: various species of aphids on strawbery (figure 38, n, o, p, q), including Chaetosiphon fragaefolii, Aphis gossypii, Macrosiphum euphorbiae and Myzus persicae. Regardind to identification they are 1) small (2 mm long) , soft bodied, slow moving; 2) green, yellowish green, pink or gray in colour and variable in shape; 3) Cornicles resemble tailpipes at the base of the abdomen; 4) Adults may or may not have wings; 5) Nymphs resemble the wingless adults; 6) Symptoms include stunted and malformed plants; 7) Black sooty mould forms on the aphids secretions known as honeydew, this can coat leaves and developing fruit; 8) Most damage caused by the transmission of viruses.
They are often confused With potato leafhopper (Empoasca fabae Harris, 1841) and tarnished plant bug (Lygus lineolaris Palisot de Beauvois, 1818). About the activity they are generally, aphids overwinter as eggs. Active stages present from early spring through to late summer. Winged forms migrate away from heavy infestations to start new colonies. This aphids can be found on new shoots, the undersides of leaves and on buds while they are still in the crown. Cast skins from previous moults may be present on leaves after aphids have left. The honeydew can be attractive to ants.
Potato Leafhopper (Empoasca fabae Harris, 1841): adults are long and narrow in shape, abdomens tapered, green with long folded wings, fly away quickly (Figure 38, r). Nymphs are long and narrow in shape, light green and walk sideways across the leaf when disturbed (Figure 38, s). Older nymphs develop wingpads on the thorax. Nymphs are light green and walk sideways across the leaf when disturbed. Leafhoppers suck sap from the leaves, which causes yellow mottling around the edges. They also inject a toxin into the plant while they feed which reduces shoot vigour. Affected leaves turn pale green and curl downward at the margins. Potato Leafhopper is often confused With aphids, tarnished plant bugs and herbicide injury. About the period of activity, potato leafhoppers overwinter in the southern United States and are carried northwards on air currents. They migrate into new plantings of strawberries in early or mid June, often after the first cut of hay. Multiple generations are active throughout the summer and early fall. Focus on new (first year) plantings. Examine new leaves for leaf curl and yellowing (Figure 38 t). Look for leafhopper nymphs on the underside of the leaf. "Governor" Simcoe" and "Jewel" are good varieties to check for first signs of damage. There are no thresholds established for potato leafhopper. Consider control if there are one or two nymphs per leaf and leaf curl is evident.
Figure 38 - Adults of Otiorhynchus ovatus (a), Otiorhynchus sulcatus (b), Anthonomus signatus (c), damage on crown (d) and leaves (e); larvae (f) and pupa (g) in soil; Root weevil damage in open field (h).
Flower damage caused by strawberry clipper weevil with the presence of adult (i); clipped bud from strawberry clipper weevils (l) and older damage from strawberry clipper weevil consisting in dried up bud (m).
Aphids attack on strawberry (n); cast skins of aphids (o); black sooty mold left behind by aphids (p); balloon-shaped brittle skins of parasitized aphids (q).
Potato leafhopper adult (r) and nymph (s). Potato leafhopper leaf curl and marginal yellowing from feeding (t).
Tarnished plant bug whose scientific name is Lygus lineolaris (Palisot de Beauvois, 1818). The taxonomy is Kingdom Animalia C. Linnaeus, 1758; Epitheliozoa Ax, 1996 Eumetazoa Bütschli, 1910; Bilateria Hatschek, 1888; Eubilateria Ax, 1987;
Protostomia Grobben, 1908; Ecdysozoa A.M.A. Aguinaldo et al., 1997; Superphylum Panarthropoda; Mandibulata; Crustaceomorpha Chernyshev, 1960;
Subphylum Pancrustacea Zrzavý et al., 1997; Altocrustacea; Miracrustacea; Superclass Hexapoda Latreille, 1825; Subclass Dicondylia;
Infraclass Pterygota; Metapterygota; Neoptera; Eumetabola; Paraneoptera; Superorder Condylognatha;
Order Hemiptera C. Linnaeus, 1758; Heteropterida; Suborder Heteroptera; Infraorder Cimicomorpha; Superfamily Miroidea;
Family Miridae Hahn, 1831; Genere Lygus Hahn, 1833; Species Lygus lineolaris (Palisot, 1818).
Adults are oval in shape 4-6 mm long, green to brown in colour with triangular markings in the middle of the back, last on the right). Fly quickly when disturbed. Nymphs are small in size, ranging from 1 to 5 mm in length, depending on the instar. They are green in colour and darken as they mature. Typically the third instar has five black dorsal spots and is beginning to develop wing pads (Figure 39, a, the first 4 from left). Plant bugs have mouth parts that pierce and suck on plant juices. They feed on strawberry fruit and bloom, which causes misshapen fruit described as catfacing or button berry (Figure 39, b). Lygus bug infestations lead to severe distortion of the fruit, known as "catfacing," that renders the fruit unmarketable. Lygus bugs are most destructive in the early summer, and cause damage similar to that of frost injury in winter plantings. As a strawberry pest, the tarnished plant bug often causes considerable loss by feeding on the seeds of the young fruits before the receptacle expands. In feeding, it sucks out plant juices. The damaged seeds cause the receptacle to expand unevenly. Thus, berries that are injured remain small, have a woody texture, and fail to mature. Berries become knobbed with seeds grouped apically and are unsalable. This injury is known as "button berry" and is a serious problem in some areas. Later-maturing varieties are more severely affected. Although several plant bugs (Lygus spp. and others) may be involved, the tarnished plant bug appears to be the chief culprit.
Often tarnished plant bug is confused With frost poor pollination, potato leafhoppers, aphids. Overwintering plant bug adults move into strawberry plantings in early spring (April). Nymphs appear during strawberry bloom and are active through to the first harvest. There are several generations per year and all instars can be present throughout the summer. Monitoring to identify nymphs is critical to reduce damage, but nymphs can be difficult to find due to their size, colour and speed. The only key symptoms of tarnished plant bug infestation are damaged fruit. Look for tarnished plant bugs at first bloom (late May) through to the green fruit stage. Walk in a W pattern across a block. Tap the blossom clusters into a white tray or dish. Count the number of nymphs per 100 clusters.
A faster method that can be used when populations are very low or very high is sequential sampling. For sequential sampling count the number of infested clusters, not the number of nymphs per cluster.
White grubs (Phyllophaga spp.Harris, 1827: it is a Coleoptera: Scarabaeidae Melolonthinae. Larvae of June beetles, European chafers, and Japanese beetles are all known as white grubs. Adult beetles are hard-shelled, block-shaped beetles which fly at night and are seldom seen in strawberry fields (Figure 39, a,and Figure 39, c, d and e).
The larvae are found in the soil; they are C-shaped, with a tan or brown head capsule and six prominent spiny legs. Symptoms of white grub injury on strawberry plants include stunted growth and plant dieback. Often confused With root weevil, Verticillium wilt and black root rot. June beetle adults are active in late May and early June, European chafer adults are active in June and Japanese beetles adults are active in late July and August. Eggs are laid in grassy places. The eggs hatch into larvae, or white grubs and feed on plant roots. European chafer and Japanese beetle larvae feed in late summer and again in the spring, until adults emerge. June beetle larvae remain in the soil for three seasons and feed on plant roots throughout each growing season. First-year plantings are most susceptible to damage. Where plants show poor vigour or have wilted, collapsed and died, check the roots for damage and the soil around the plants for grubs.
Figure 39 - Different nynhal instars of Tarnished plant bug nymph (a, the first 4 from left); typically the third instar has five black dorsal spots and is beginning to develop wing pads (a, fourth from left); adult of Lygus lineolaris (a, fifth from left). Plant bugs have mouth parts that pierce and suck on plant juices. They feed on strawberry fruit and bloom, which causes misshapen fruit described as catfacing or button berry.
Adult of Phyllophaga spp. (c); larva typically C-shaped (d); White grub damage to new planting (e).
African cotton leafworm or Egyptian cotton leafworm (Spodoptera littoralis Boisduval, 1833) also known as the Mediterranean brocade. The taxonomy of Spodoptera littoralis is Class Insecta C. Linnaeus, 1758; Subclass Dicondylia; Infraclass Pterygota; Metapterygota; Neoptera; Eumetabola; Holometabola; Superorder Panorpida; Amphiesmenoptera; Order Lepidoptera C. Linnaeus, 1758; Suborder Glossata/i> Fabricius, 1775; Coelolepida Nielsen & Kristensen, 1996; Myoglossata Kristensen & Nielsen, 1981; Neolepidoptera Packard, 1895; Infraorder Heteroneura Tillyard, 1918; Eulepidoptera Kiriakoff, 1948; Ditrysia Börner, 1925; Apoditrysia Minet, 1983; Obtectomera Minet, 1986; Macroheterocera Chapman, 1893; Superfamily Noctuoidea Latreille, 1809; Family Noctuidae Latreille, 1809; Subfamily Noctuinaeᵀ Latreille, 1809; Tribe Prodeniini Forbes, 1954; Genus Spodoptera Guenée, 1852.
It is a moth found widely in Africa and Mediterranean Europe. It has been recorded at least six times in the UK, either an immigrant or as an accidental import. It is often a pest on vegetables, fruits, flowers and other crops. The taxonomy is the following: Kingdom: Animalia; Phylum: Arthropoda; Class: Insecta; Order: Lepidoptera; Family: Noctuidae; Genus: Spodoptera.
Moth with grey-brown body, 15-20 mm long; wingspan 30-38 mm; forewings grey to reddish brown with paler lines along the veins (in males, bluish areas occur on the wing base and tip); the ocellus is marked by two or three oblique whitish stripes. Hindwings are greyish white, irridescent with grey margins and usually lack darker veins. When newly formed, pupae are green with a reddish colour on the abdomen, turining dark reddish-brown after a few hours. The general shape is cylindrical, 14-20 x 5 mm, tapering towards the posterior segments of the abdomen. The last segment ends in two strong straight hooks. Larvae grow to 40-45 mm and are hairless, cylindrical, tapering towards the posterior and variable in colour (blackish-grey to dark green, becoming reddish-brown or whitish-yellow). The sides of the body have dark and light longitudinal bands; dorsal side with two dark semilunar spots laterally on each segment, except for the prothorax; spots on the first and eighth abdominal segments larger than the others, interrupting the lateral lines on the first segment. Eggs are spherical, somewhat flattened, 0.6 mm in diameter, laid in clusters arranged in more or less regular rows in one to three layers, with hair scales derived from the tip of the abdomen of the female moth. Usually whitish-yellow in colour, changing to black just prior to hatching, due to the big head of the larva showing through the transparent shell
Damage arises from extensive feeding by larvae, leading to complete stripping of the plants. Female moths lay most of their egg masses (20-1000 eggs) on the lower surface of younger leaves or upper parts of the plant. The larvae feed mainly in the dark, although this behaviour pattern may be less noticeable in early instars and less 50% of the nocturnal larval population consisted of early instar larvae. In summer the majority of fifth- and sixth-instar larvae leave the plants during mid-morning until sunset, returning to climb the plant at night. Third- and fourth-instars rest on the plant and remain stationary unless overcrowded.
On pupation the fully grown larva pushes the loose surface of the soil downwards until it reaches more solid ground 3-5 cm deep. It then creates a clay 'cell' or cocoon in which it usually pupates within 5-6 hours.
Emergence of adult moths occurs at night and they have a life span of 5-10 days. The reproductive capacity, egg facility and life span of moths are affected by the difference in ages between males and females. The highest ratio of egg fertility was obtained by mating between 4-day-old males with fresh females. There is also a correlation between the host plant and the longevity and fecundity of Spodoptera litoralis. The majority of adults mate on the first night of emergence, copulation lasting for 20 minutes to 2 hours. Approximately 50% of mated females lay their eggs on the same night of mating, before. Adults fly at night, mostly between 20.00 and midnight. Flight activity is governed by atmospheric conditions, increases in relative humidity and decreases in air temperature inducing flight. The flight range during a 4-hour-period can be up to 1.5 km.
The moths have chemoreceptors on the ventral surface of the tarsi and the distal portion of the proboscis. These are highly sensitive and respond to a certain number of sugars mainly present in nectar. Pheromones (comprising of tetradecadien-1-ol acetates) have been isolated and successfully used in traps.
The minimum constant temperature for normal development in all stages is 13-14 °C. Resistance to cold generally increases through the larval stages and is greatest in the pupal stage.At 18 °C, egg, larval and pupal stages last 9, 34 and 27 days, respectively. At 36° C, egg, larval and pupal stages last 2, 10 and 8 days, respectively.
About the biological control, numerous studies have been carried out on possible biological control of Spodoptera littoralis. Parasitoids (braconids, encyrtids, tachinids and ichneumonids) and predators have been extensively documented. A nuclear polyhedrosis virus has been evaluated, whereas fungi and microsporidia have also been recorded as pathogens. Parasitic nematodes such asNeoaplectana carpocapsae have also been evaluated. However, direct use of these biocontrol agents has not been commercailized. Treatment with Bacillus thuringiensis has been used, but only some strains are effective as Spodoptera littoralis is resistant to many strains.
The chemical control of Spodoptera littoralis has been extensively reported, especially in relation to cotton in Egypt. Numerous organophosphorus, synthetic pyrethroids and other insecticides have been used, with appearance of resistance and cross resistance in many. However, compulsory limitation of the application of synthetic pyrethroids to one per year on cotton in Egypt has stopped the appearance of new resistance. Chemicals used against Spodoptera littoralis also include insect growth regulators. There is interest in various antifeedant compounds or extracts, and in natural products, such as azadirachtin and neem extracts.
Integrated pest management (IPM) techniques, favouring beneficial arthropods. These involve hand collection of egg masses, use of microbial pesticides and insect growth regulators and slow-release pheromone formulations for mating disruption. If these measures are taken, relatively few applications of conventional insecticides are necessary. Damage thresholds have been established. Pheromones have also been used for mass trapping using a lure and kill strategy and for monitoring populations.
Figure 40 - Spodoptera littoralis adult, wingspan 30-38 mm (a), eggs (b), larva (c), and pupae (d). Damages on leaf(e).
Strawberry leafroller caused by Choristoneura lafauryana (Ragonot, 1875) of which are shown adult (f) and adult wingspan of about 18-24 mm (g); larva (h) and eggs that are deposited in elongate batches of 70-100 eggs on the upper surface of the leaves of the food plant (i).
Strawberry leafroller whose scientific name is (Choristoneura lafauryana (Ragonot, 1875). The taxonomy of Choristoneura lafauryana is Class Insecta C. Linnaeus, 1758; Subclass Dicondylia; Infraclass Pterygota; Metapterygota; Neoptera; Eumetabola; Holometabola; Superorder Panorpida; Amphiesmenoptera; Order Lepidoptera C. Linnaeus, 1758; Suborder Glossata Fabricius, 1775; Coelolepida Nielsen & Kristensen, 1996; Myoglossata Kristensen & Nielsen, 1981; Neolepidoptera Packard, 1895; Infraorder Heteroneura Tillyard, 1918; Eulepidoptera Kiriakoff, 1948; Ditrysia Börner, 1925; Apoditrysia Minet, 1983; Superfamily Tortricoidea Latreille, 1802; Family Tortricidae Latreille, 1802; Subfamily Tortricinae; Genus Choristoneura Lederer, 1859; Species Choristoneura lafauryana (Ragonot, 1875).
This is a species of moth that was found in Spain, Great Britain, the Netherlands, Belgium, France, Germany, Switzerland, Italy, Romania and Russia. In the east, the range extends to China (Heilongjiang, Jilin, Liaoning), Korea and Japan. The wingspan is 1821 mm for males and 2024 mm for females. Adults have been recorded on wing from July to August in western Europe (Figure 40, f). The larvae feed on Artemisia (including Artemisia montana), Cirsium, Lespedeza, Ribes, Myrica (including Myrica gale), Forsythia, Larix, Fragaria (including Fragaria x ananassa), Pyrus and Salix species, as well as Rhododendron tomentosa, Glycine max, Medicago sativa, Trifolium repens, Morella rubra, Boehmeria nivea, Malus pumila and Malus sylvestris. They live between leaves and shoots spun together with silk. Larva average length 25 mm; head pale yellowish brown mixed with brownish or yellowish green; region of stemmata black; body yellowish green with a darker green dorsal line; prothoracic plate and anal plate pale yellowish brown or dark green; pinacula paler than integument, rather inconspicuous. Anal fork well developed (Figure 40, h). Eggs are deposited in elongate batches of 70-100 eggs on the upper surface of the leaves of the food plant.
They hatch in about 10 to 14 days. There are 2 generations per year. Adult strawberry leafroller is reddish brown with a distinctive yellow marking on the forewings, and a wingspan of about 12 mm (Figure 40, g). They emerge in April and May and deposit eggs (translucent) on the lower surface of the leaves.
In Minnesota, however, the strawberry leafroller is specific to strawberries, raspberries, and blackberries.
There is an other species of tortricids causing leaf-rolling in strawberry:
Ancylis comptana (Frölich, 1828) causing Strawberry leafroller or Comptan's Ancylis Moth is a moth of the Tortricidae family. It is found from the United Kingdom and Scandinavia to northern Spain and Turkey, Asia Minor, Kazakhstan, Uzbekistan, Russia, China, Mongolia, Korea and Japan. In North America, it is represented by ssp. fragariae. The wingspan is 1114 mm. Adults are on wing from April to June and from mid July till September. There are two generations per year in Europe. In the northern United States, moths of the first generation fly from the end of March to April and those of the second in late May and June. Here, a third or sometimes even a fourth generation occurs, flying in August and from September to October. The larvae feed on Sanguisorba minor, Potentilla, Fragaria, Teucrium, Rosa, Dryas octopetala, Rubus idaeus, Rubus icaesius and Thymus. The larvae damage soft fruits, especially strawberry but also raspberry. The species has become an important pest of strawberries on some locations in the United States.
Leafrollers are seldom a pest on strawberries, and treatment is usually not necessary.
Western Flower Thrips (Figure 41): The scientific name is Frankliniella occidentalis Pergande, 1895). The taxonomy is the following: Kingdom: Animalia C. Linnaeus, 1758; Epitheliozoa Ax, 1996; Subkingdom Eumetazoa Bütschli, 1910; Tree Bilateria Hatschek, 1888; Phylum Arthropoda Latreille, 1829; Subphylum Tracheata; Superclass Hexapoda Latreille, 1825; Class Insecta C. Linnaeus, 1758; Subclass Dicondylia; Infraclass Pterygota; Cohort Exopterygota; Subcohort Neoptera; Eumetabola; Paraneoptera; Superorder Condylognatha; Section Thysanopteroidea; Order Thysanoptera Haliday, 1836; Suborder Terebrantia Haliday, 1836; Family Thripidae Stevens, 1829; Subfamily Thripinae; Genus Frankliniella Karny, 1910.; Species Frankliniella occidentalis (Pergande, 1895).
Information for the parasite identification:
The attack of Frankliniella occidentalis often can be confused with: Cyclamen mite damage (Figure 42), Two-spotted spider mites (Figure 42), and Powdery mildew (Figure 34 and Figure 35)
- Found in flowers and on fruit.
- Tiny, yellow-brown insects.
- Long and narrow in shape, threadlike.
- Less than 2 mm long.
- Nymphs resemble adults in shape and colouring.
- Adults have fringe of hairs on their wings (visible with microscope) .
- Thrips have rasping sucking mouthparts and cause damage by scraping of plant tissue.
- Close inspection of damaged strawberry fruit reveals a necrotic flecking or bronzing of the seeds and fruits, especially beneath the calyx.
- Symptoms of fruit bronzing occur when king berries reach 5- 10 mm (1/5- 2/5 in.) in diameter.
- The entire fruit may become bronzed and cracked.
- Seeds are prominent.
Thrips do not overwinter but migrate each spring on air currents from the south. They are attracted to white flowers and therefore to strawberry bloom that is open when the thrips arrive. They do not cause problems on strawberries every year.
Shake blossom clusters into a white tray or dish. If high numbers of yellow thrips appear, check developing blossoms and fruit for injury.
Use a hand lens to look closely for thrips. Breathe gently on blossoms to encourage thrips to move out of the bloom. Check under the calyx of small green fruit for thrips and rusty discolouration.
There are no thresholds Western Flower Thrips. A threshold of 10 thrips per bloom is used in California. A suggested limit is 25 thrips/50 fruit and 5 thrips/ 50 fruit in New Brunswick, in Quebec 2-10% of fruit with bronzing (Figure 41, bottom right).
The western flower thrips is an important pest insect in agriculture. This species of thrips is native to the South-western United States but has spread to other continents, including Europe, Australia (where it was identified in May 1993), and South America via transport of infested plant material. It has been documented to feed on over 500 different species of host plants, including a large number of fruit, vegetable, and ornamental crops. The adult male is about 1 mm long; the female is slightly larger, about 1.4 mm in length. Most western flower thrips are female and reproduce by arrhenotokous parthenogenesis; i.e. females can produce males from unfertilized eggs, but females arise only from fertilized eggs. Males are rare, and are always pale yellow, while females vary in color, often by season, from red to yellow to dark brown. Each adult is elongated and thin, with two pairs of long wings. The eggs are oval or kidney-shaped, white, and about 0.2 mm long. The nymph is yellowish in colour with red eyes.
The life cycle of the western flower thrips varies in length due to temperature, with the adult living from two to five or more weeks, and the nymph stage lasting from five to 20 days. Each female may lay 40 to over 100 eggs in the tissues of the plant, often in the flower, but also in the fruit or foliage. The newly hatched nymph feeds on the plant for two of its instars, then falls off the plant to complete its other two instar stages. The insect damages the plant in several ways. The major damage is caused by the adult ovipositing in the plant tissue. The plant is also injured by feeding, which leaves holes and areas of silvery discoloration when the plant reacts to the insect's saliva. Nymphs feed heavily on new fruit just beginning to develop from the flower. The western flower thrips is also the major vector of tomato spotted wilt virus, a serious plant disease.
Western flower thrips are a year-round pest, but is less destructive during wet weather. Damage can be reduced by growing barriers of nonhost plants around crops and by eliminating reservoir plants, plants to which the thrips are especially attracted, such as jimson weed. The thrips natural enemies include pirate bugs of genus Orius. Other agents show promise as biological pest control, including the fungus Metarhizium anisopliae.
Flower-feeding thrips are routinely attracted to bright floral colours, especially white, blue, and yellow, and will land and attempt to feed. Some flower thrips will "bite" humans wearing clothing with such bright colours, though no species feed on blood; such biting does not result in any known disease transmission, but skin irritations are known to occur.
Figure 41 - Western flower thrips adult; note the fringed wings are folded over its back (top left). The adult male is about 1 mm long; the female is slightly larger, about 1.4 mm in length. Frankliniella occidentalis nymph (top right). Frankliniella occidentalis attack of the flowers (bottom left). Fruit with bronzing (Figure 41, bottom right).
The most important for strawberry are represented od spider mites of the genus Tetranychus Dufour, 1832. This genus is so framed taxonomically: Natura; Mundus Plinius; Naturalia; Biota; Domain Eukaryota Chatton, 1925; Unikonta; Opisthokonta Cavalier-Smith, 1987; Holozoa; Kingdom Animalia C. Linnaeus, 1758; Epitheliozoa Ax, 1996; Eumetazoa Bütschli, 1910; Bilateria Hatschek, 1888; Eubilateria Ax, 1987; Protostomia Grobben, 1908; Ecdysozoa A.M.A. Aguinaldo et a., 1997; Superphylum Panarthropoda; Phylum Arthropoda Latreille, 1829; Euarthropoda; Subphylum Arachnomorpha Heider, 1913; Infraphylum Cheliceriformes; Superclass Chelicerata ; Epiclass Euchelicerata Weygoldt & Paulus, 1979; Class Arachnida Cuvier, 1812; Micrura Hansen & Sørensen, 1904; Acaromorpha Dubinin, 1957; Subclass Acari Leach, 1817; Superorder Acariformes Zakhvatkin, 1952; Order Actinedida van der Hammen, 1968; Suborder Eleutherengona Oudemans, 1909; Section Raphignathae Superfamily Tetranychoidea Donnadieu, 1876; Family Tetranychidae Donnadieu, 1876; Subfamily Tetranychinae Donnadieu, 1876; Genus Tetranychus Dufour, 1832.
We describe some species of mites very harmful for strawberry (Figure 42):
Twospotted spider mite: its scintific name is (Tetranychus urticae Koch, 1836). Twospotted spider mite eggs are about 0.14 mm in diameter and are laid on the undersides of leaves. They are spherical, clear, and colorless when laid but become pearly white as hatch approaches.
Nymphs, adult males, and reproductive adult females are oval and generally yellow or greenish. There are one or more dark spots on each side of their bodies, and the top of the abdomen is free of spots.
Adult female twospotted spider mites may stop reproduction during the coldest winter months in production areas of colder inland valleys. Diapause is indicated by a change in color to bright orange. In coastal growing areas it is rare to have a significant proportion of the population undergo diapause. Mating and egg laying typically occur year round in all coastal strawberry-growing regions.
Twospotted spider mites are sap sucking pests that feed on the underside of leaves. The first signs of damage are speckling and mottling on the surface of leaves. In heavy infestations, leaves turn purple, with white webbing between leaves. Affected plants are stunted, low-yielding and the fruit size and quality are ` poor. Outbreaks of this pest are favoured by warm, dry conditions from spring onwards (Figure 42).
Carmine spider mite: the scientific name is Tetranychus cinnabarinus Boisduval, 1867. The carmine spider mite has the largest host range of all Tetranychidae species and is undoubtedly of greatest economic importance. Adults and nymphs feed primarily on the undersides of the leaves. The upper surface of the leaves becomes stippled with little dots that are the feeding punctures. The mites tend to feed in "pockets" often near the midrib and veins. Silk webbing produced by these mites is usually visible. The leaves eventually become bleached and discolored and may fall off. The carmine spider mite normally completes a life cycle from egg to adult in about a week. All stages of this mite are present throughput the year. Reproduction is most favorable when the weather is hot and dry. Eggs are spherical, shiny, straw colored, and hatch in 3 days. They are only about 1 mm in diameter. They are laid singly on the underside of the leaf surface or attached to the silken webs spun by the adults. Larvae are slightly larger than the egg, pinkish, and have three pairs of legs. This stage lasts a short time, perhaps a day. There are two nymphal stages, the protonymph and deutonymph. The nymphal stage differs from the larval stage by being slightly larger, reddish or greenish, and having 4 pairs of legs. This nymphal stage lasts about 4 days. Adult females are about 0,5 mm long, reddish, and more or less elliptical. The males are slightly smaller and wedge shaped. They have a black spot on either side of their relatively colorless bodies. The adult female may live for up to 24 days and lay 200 eggs. The major natural predator of the carmine spider mite is a Stethorus beetle. This beetle feeds on all stages of these mites and in laboratory conditions each individual beetle consumed an average of 2,400 mites. The feeding activity of the predatory beetle is greatest in crops with smooth leaves on their undersides. There are a number of other ladybird beetles which feed on mites, but they are not as effective as Stethorus. A number of predacious mites, such as Phytoseiulus macropilis (Banks, 1904), are also effective on many crops in controlling carmine spider mites. There are also several species of predatory thrips that feed on mites.
Strawberry spider mite (Tetranychus turkestani Ugarov et Nikolskii, 1937): Both strawberry and twospotted spider mites look similar. Twospotted spider mite is the predominant species in strawberries. Strawberry spider mite occurs in some areas, with mixed populations of both twospotted and strawberry spider mites seen particularly during the warmer parts of the production season. Adult female has an oval shape and a size approximately 0.50 mm long and 0.30 mm wide. The male has a much lower size and a narrower body, with the pointed abdomen and proportionately longer legs. The coloration of the female is diverse and can be yellow, green, red-orange or crimson, but always with two dark spots on the back side of the chest. In the male coloration is paler.
Lewis spider mite: the scientific name is Eotetranychus lewisi McGregor. Lewis spider mites have been seen on strawberries and growers appear to be noticing increased infestations in the recent years in U.S.A. Environment, natural enemies, cropping patterns, pesticide usage and other agronomic practices are among the factors that influence the status of pests. Males are about 0.25 mm and females are about 0.36 mm long. Species identification is tricky and requires both sexes to be examined microscopically. They can be confused with twospotted spider mite in their general appearance. But, comparing adult females, lewis mites are smaller than twospotted spider mite and have several small spots on their body while twospotted spider mite have a single dark spot on either side of the body. Lewis mite has five life stages: egg, larva, protonymph, deutonymph and adult. Eggs are round, whitish to light orange. Females lay 60-90 eggs over a period of about a month. It takes about 12-14 days from egg to adult stage at 21 °C.
Cyclamen mites: the scientific name is Phytonemus pallidus Banks, 1901. Adult mites are microscopic. Eggs are clear, oval and marked with characteristic rows of white tubercles that appear gem-like under proper lighting. Immatures resemble adults, although smaller in size. Adults have 4 pair of legs, with 2 pair toward the front of the body and 2 near the rear (Figure 42,e). The middle of the body may be constricted to look waist-like. Males are shorter, broad and have longer hind legs. The life cycle takes from 4 to 10 days. On strawberry plants the leaf petioles are short, blades are small, thickened and wrinkled, and total growth is stunted (Figure 42, h, i, l).
Figure 42 - Spider mites regarding the strawberry: adults of Twospotted spider mite (a), Carmine spider mite (b), Strawberry spider mite (c), Lewis spider mite (d), and Cyclamen mites (e). Coloration faded and bronze of leaves attacked by red spider mite (f). Plant severely debilitated by red spider mite (g). Dried plant due to Cyclamen mites attack (h). Leaf curl due to Cyclamen mites attack (i). Plant with serious damage due to pale mite (l).
The spider mites management consists:
The attacks of spider mite regard the protected cultivation with damage that can be substantial if you do not do a constant monitoring the pests and does not prevent the conditions favorable to its development.
- Monitor crop for mites.
- Control weeds in and around crop.
- Introduce and promote beneficial organisms such as:
- Phytoseiulus persimilis Athias-Henriot, 1957;
- Phytoseiulus fragariae Denmark & Schicha, 1983 (less effective than Phytoseiulus persimilis);
- Amblyseius californicus (McGregor, 1954) a very commonly used predatory mite;
- Amblyseius cucumeris Oudemans, 1930;
- Typhlodromips swirskii (Athias-Henriot, 1962);
- Feltiella acarisuga (Vallot, 1827);
- Stethorus punctillum Weise, 1891;
- Macrolophus caliginosus Wagner;
- Scolothrips sexmaculatus Pergande, 1890.
- Apply insecticides if necessary. Rotate chemicals, from different chemical groups, to prevent resistance.
- Use of resistant strawberry varieties
The pest usually colonizes the underside of the leaf, where you can easily verify the simultaneous presence of egg masses, of nymphs and adults. After, the infestation can also affect the upper side of the leaf up to cover the plant with a thick canvas sericea which houses the various stages of the spider mite.
Bites feeding spiders cause the appearance on the upper side of the leaf of fine discolored punctuations that, with the progress of the attack, converge to give to the leaves a classic faded color with shades of bronze. The affected plants remain highly debilitated in their vegetative development.
Often the initial attacks involve small foci of infestation, consist of a few plants, for then to extend to higher proportions surface of the field.
On crops in the greenhouse and tunnel, you will have to avoid the persistence over long periods of time of conditions of high temperature and low relative humidity, inducing a constant ventilation and a gradual painting of white of the plastic sheets starting on the spring until the summer.
It must therefore constantly monitor the evolution of the population of the pest; in cultivations from plants exposed in pre-transplant at cold treatment are obtained, in general, excellent results by running a cleaning in winter of the strawberry field, combining in a mixture the chemical against the eggs with a larvicidal product plus a product with an action adulticide .
During the deleting of the old and sicki leaves from the plants good practice to remove the plant debris from the field, which are generally a large inoculum of the pest. A second treatment will perform, once ascertained the presence, even limited, of the pest, positioning it as close as possible to the collection, using products that naturally possess a short time of shortage, also combining in this case a product against the eggs,the larvae and adulticide. This is to avoid having to intervene in the harvest begun.
It is always advisable to use selective products against natural predators. If you follow the program of biological and/or integrated with the use of mites phytoseiid, predators of spider mites, simply one winter treatment followed by launch of auxiliaries, when temperatures become favorable (18-20 individuals per square meter repeated throwing).
The selective products registered on the crop can be used in case of occurrence of outbreaks of infestation during collection, for performing localized treatments.
Abiotic factors limiting production
- Cold and frost injury (Figure 43): strawberry buds, blossoms, and immature fruit can be damaged by cold temperatures. Frost injury is more common in low lying areas of the field. Straw mulch between the rows may contribute to lower field temperatures, preventing the soil from warming up during the day. The critical temperature for injury depends on the variety, the stage of development, and the duration of adverse conditions. Freezing damage to crowns is common and can kill plants. Frost-damaged blossoms may dry-up or drop before forming fruit or misshapen fruit may be produced. Damage can be reduced by using sprinkler irrigation during low temperature periods, and row covers. Late blooming or frost-resistant varieties are less prone to blossom frost injury.
Strawberry flowers are particularly susceptible to frost damage because the plant is low to the ground, and the blossoms open toward the sky. Straw mulch between the rows contributes to lower field temperatures, because it prevents the soil from warming very much during the day. There are three types of frost that can cause damage to strawberry plants: radiation frost, radiation freeze and advective freeze.
Radiation frost occurs with an air temperature as high as 4 °C or 5 °C if there is a low dew point and no wind, because heat is lost from leaves and flowers more quickly than it is lost from the air. This type of frost is less likely to occur on nights when cloud cover traps the heat, or when a light wind (> 6 km/hr) mixes warmer upper air with colder lower air near the strawberry plants.
Radiation freeze occurs when a cold air mass moves in with minimum wind. Here, the air is usually below freezing and, as heat radiates from the plant, the flower buds freeze. If the dew point is low enough, there may not be any frost visible, just plant tissue damage.
Advective freeze occurs when a cold, dry air mass moves in, accompanied by wind. Here, freezing occurs very rapidly, which makes frost protection very difficult.
Symptoms vary with the stage of plant development, the actual temperature and the length of time damaging temperatures occur. Symptoms can include:
1) Pistils in the center of blossoms turn black or brown.
2) No fruit develops or misshapen fruit is produced.
3) Tips and edges of new leaves may look water-soaked, and then turn brown and dry.
4) Sometimes leaf tissue is damaged but not killed by frost; these leaves are misshapen, because the damaged tissue can not expand normally.
5) Sometimes the lower leaf surface separates from the upper leaf surface, giving the leaf a crinkled appearance.
Frost injury often confused with tarnished plant bug injury (Figure 39) and cyclamen mite damage (Figure 42, e and h)
Strawberry buds, blossoms and immature fruit can all be damaged by cold. The critical temperature for injury depends on several factors, including the variety, the stage of development and climatic conditions such as temperature, wind speed and duration of adverse conditions. Strawberry flowers are most sensitive to frost injury immediately before and during opening. At this stage, temperatures lower than -2 °C will cause injury. When flowers are in tight clusters in the crown, they will tolerate temperatures as low as -5.5° C. The critical temperature for plant tissue at which injury occurs is difficult to measure and varies from variety to variety.
To control the cold and frost injury to apply the following management:
a) Growers use irrigation to prevent frost damage to plant tissue. As water freezes, it releases enough heat to protect the plants from frost damage. A thin film of water must be constantly freezing during the frost event. If ice is cloudy , rather than clear, not enough water was applied and frost damage can still occur.
b) Frost injury usually occurs to primary flowers because these are the first to open. Primary flowers also produce the largest and most valuable fruit.
c) Frost-damaged tissue is very susceptible to Botrytis grey mould. In this case, Botrytis is a problem for a few pickings, as the fruit from frost damaged bloom develops.
Figure 43 - Cold and frost injury: misshapen fruit developing from partially frozen blooms (a). Recent frost injury to leaves (b). Blackened flower parts (c). Misshapen fruit developing from partially frozen blooms (d).
- High temperatures and over-exposure of fruits to the sun (sunscald): sunscald is caused by high temperatures and over-exposure of strawberry fruit to the sun. Symptoms are more common when hot sunny weather occurs after a prolonged period of cool cloudy weather. Symptoms appear on the upper side of fruit, near the calyx, just before ripening. The fruit becomes pale and mushy at first, eventually drying down to a distinct, firm, bleached lesion ranging in colour from pink to off-grey (Figure 44). Berries growing on the south or west side of rows, and those without adequate foliage canopy, are most susceptible. Some varieties are more susceptible than others.
This termic disorder can be confused With leather rot (Figure ) and anthracnose (Figure 37).
Figure 44 - Sunscald. The fruits are pale and mushy at first, eventually drying down to a distinct, firm, decolored lesion ranging in colour from pink to off-grey. Symptoms of recent sunburn or sunscald on fruit (a) and sunscald starting to dry up on fruit (b).
- June yellows: it is a non-infectious genetic disorder that develops in certain varieties.
To identify the disorder carry out the following observations:
1) Yellow or white streaking and mottling of leaves.
2) Symptoms worsen as the planting ages (i.e. worse in 3 year old plantings than 1 year old plantings).
3) Symptoms are most apparent in early spring, and less so when weather warms up.
4) Eventually causes stunting and a reduction in fruit production.
5) Symptoms of June yellows are consistently present in almost every plant in the affected block.
The symptoms often are confused with:
a) Herbicide damage;
b) Nutrient deficiency.
June yellows can be distinguished from these problems by the pattern of injury in the field and by the varieties affected.
Are given some management notes:
Affected plants never recover. There is no known control for June yellows.
Do not propagate from plants affected by June yellows.
Only some the varieties such as "Glooscap" and "Mesabi" are known to develop june yellows.
Figure 45 - June yellows on foliage (a and b). Streaking on foliage (b).
- Uneven ripening: this condition is thought to develop when high temperatures occur during the fruit ripening stage affecting the enzymes that cause normal pigmentation in ripe fruit. Fruit which are exposed to high temperatures earlier in their development are not as susceptible as fruit exposed to cool temperatures early on.
The variety "Cavendish" is especially susceptible to this condition, where white shoulders and blotches occur on otherwise ripe fruit. Although fruit is ripe and sweet, colour does not develop on certain areas of the fruit (Figure 46).
"Cavendish" (Nova Scotia) is a high yielding, high quality berry in a good year. However, high temperatures during ripening can cause uneven ripening that can be a real problem.
Figure 46 - Uneven coloring of the fruits of strawberry caused by abnormal pigmentation during development in the variety "Cavendish".
- Misshapen berries: berry size and shape is largely due to the number of seeds that develop on the surface of the berry. If a group of seeds does not develop, the portion of the berry under the seed will not enlarge or ripen. This results in a misshapen berry that is either pinched-in (monkey faced or cat faced), multiple-tipped, or fan-shaped (fasciated). Anything that prevents seed development can result in misshapen berries, including poor pollination,frost or hail injury to blossoms or fruit, high temperatures and drying winds during bloom, disease, insect feeding on flowers or fruits, short day length in the fall, herbicide injury, genetic factors (varieties) and nutrient imbalances.
In the Figure 47 are indicated distorted or misshaped fruits such as:
- Strawberry phyllody (a), for which Occasionally early fruit can show strawberry phyllody symptoms (small leaves sprouting around seeds on fruit). Symptoms can be similar to calcium or boron deficiency.
- Marginal leaf burn (b), the which possible causes are soil diseases such as verticillium wilt or crown rot, salt damage from the use of saline water or excess fertiliser.
- Albino fruit (c), the which possible cause is high nitrogen levels and overcast weather during fruit ripening. Symptoms can be similar to potassium deficiency.
- Poor pollination (d) the which possible causes are wet or frosty conditions during flowering, lack of bee activity and poor flower movement. Symptoms can be similar to calcium or boron deficiency on immature fruit.
Figure 47 - Distorted or misshaped fruit symptoms: strawberry phyllody (a), marginal leaf burn (b), albino fruit (c), and poor pollination (d).
- Herbicide injury: herbicide injury is sometimes confused with disease symptoms or insect damage. Drift or contamination with 2,4-D herbicide may cause deformed fruit. Symptoms of terbacil, simazine or other herbicide injury may resemble fungal or viral diseases.
Following are reported the symptoms caused by anormal use of some herbicides (such as Clopyralid, Glyphosate, Imazethapyr, Paraquat, S-Metolachlor, Simazine, and Terbacil) on strawberry plants:
- Clopyralid is a synthetic auxins. First symptoms include bending, twisting, swelling and elongation of stems; leaf cupping and curling. Followed by: chlorosis at the growing points, growth inhibition, wilting, necrosis, and death of susceptible plants within 3-5 weeks. Low concentration may cause young leaves to look puckered (Figure 48).
Figure 48 - Symptoms caused by abnormal use of clopyralid.
Uptake and translocation regarding this herbicide consist in: 1) rapidly absorbed by foliage; 2) translocated readily throughout the plant via both xylem and phloem systems; 3) clopyralid is distributed throughout the plant to the meristem. Regarding to the persistence: 1) the half life in field is less than 30 days; 2) the residuals may injure certain crops (such as tomatoes and peppers) planted 1 year after application.
- Glyphosate is an inhibitors of 5-enolpyruvaylshikimimate-3-phosphate synthase (EPSP). Symptoms include inhibited growth, general foliar chlorosis and necrosis within 4-20 days depending on temperature at time of application, immature leaves and growing points are often the first to undergo chlorosis (Figure 49).
Figure 49 - Symptoms caused by abnormal use of glyphosate.
Uptake through foliage and Translocation throughout the plant. The persistence in field is 47 days (half life), therefore none crops can be planted or seeded directly into treated areas following application.
- Imazethapyr is an inhibitors of acetolactate synthase (ALS) and also called acetohydroxyacid synthase (AHAS). Symptoms following post-emergent application: Within an hour the inhibition of ALS enzyme leads to a rapid cessation of cell division and plant growth; within 1- 2 weeks symptoms become visible; meristematic regions are the first to experience chlorosis and necrosis followed by general foliar chlorosis and necrosis (Figure 50).
Figure 50 - Symptoms caused by abnormal use of imazethapyr.
Imazethapyr is absorbed by both roots and foliage, and the translocation in both xylem and phloem. The persistence depends on weather and soil conditions (more persistent under dry conditions) and the half-life in field is 60- 90 days. For most vegetable crops, a 22 month recropping interval is recommended.
- Paraquat symptoms following post-emergent application: within a few hours, in full sunlight, the plant wilts and dries out; in 1-3 days complete foliar necrosis occurs; injury from drift can occur and presents itself as spots of dead leaf tissue wherever there is contact by spray droplets (Figure 51).
Figure 51 - Symptoms caused by abnormal use of paraquat.
Paraquat is absorbed by foliage and green bark, with little or no translocation.
It is highly persistent but residues are tightly adsorbed and unavailable in the soil. Essentially no residual activity in soil. The half-life in field is 1000 days.
- S-Metolachlor cause the conjugation of acetyl co-enyme A. Symptoms following the pre-emergency application are that seedlings fail to emerge. Symptoms following the pre-emergency application are that the seedlings fail to emerge. Symptoms following post-emergency application are that the seedlings are deformed. Leaves may be trapped or emerge underground (Figure 52)
Figure 52 - Symptoms caused by abnormal use of s-metolachlor.
S-Metolachlor is absorbed by germinating grasses mainly through shoot just above seed. It is absorbed by germinating broadleaf weeds through roots and shoots. Translocated towards growing points. About the his persistence, the activity will normally be maintained for 10-14 weeks.
- Simazine is an inhibitors of photosynthesis at photosystem II, Site A. The first symptoms include interveinal chlorosis of leaves and yellowing of margins;
followed general foliar chlorosis and necrosis, browning of leaf tips, older leaves show more injury than new (Figure 53)
- Simazine consists of inhibitors of photosynthesis at photosystem II, Site A. The first symptoms include interveinal chlorosis of leaves, yellowing of margins of leaves. The following symptoms are the general foliar chlorosis and necrosis, browning of leaf tips and older leaves showing more injury than new (Figure 52).
Figure 53 - Symptoms caused by abnormal use of simazine.
Simazine is absorbed by roots but little or no foliar absorption and translocated upwards in xylem, accumulating in apical meristem and leaves.
About the persistence simazine have a moderate residual and half life of 30 days in fields, 60 days in ponds. Simazine is more persistent in high pH soils and the residues can injure crops one year after application.
- Terbacil consists of inhibitors of photosynthesis at photosystem II, Site A. Symptoms are foliar chlorosis, first interveinal, followed by total leaf chlorosis and eventually tissue death, inhibition of root and shoot growth and more injury potential on low organic matter soils (Figure 54).
Figure 54 - Symptoms caused by abnormal use of terbacil.
- Nutrient balance: a balance of nutrients is required for optimal growth of strawberry plants. Nutrients may be present in soil, but depending on conditions they may be unavailable for uptake, or in concentrations that are toxic to plants. Soil pH can affect the availability of nutrients, and lime is usually applied to raise pH levels in acidic soils. Leaf and soil analyses are useful to determine fertilizer requirements. Foliar sprays of micronutrients are generally recommended during the growing season if nutrient deficiency deficiency is observed.
In the context of this chapter are very important the nutrient deficiency symptoms. Plant nutrient deficiencies or toxicity during the establishment and growing season can have a major affect on fruit yield and quality. Some of the more common plant symptoms of plant nutrient disorders are the following.
- Nitrogen: it is an important nutrient in strawberry growing. During periods of rapid growth, leaves of nitrogen-deficient plants remain small and may turn from green to light green or yellow (Figure 51).
In older leaves the leaf stalk reddens and the leaf blades become brilliant red.
Fruit size is reduced, and the calyx around the fruit becomes reddish.
Figure 55 - Nitrogen deficiency on leaves (left) and on flower, where on observe a red calyx (right).
Control consists in to apply most nitrogen before planting as a soil base application and during the growing season as either foliar fertiliser or by fertigation. Table 1. Applying nitrogen between rows is not effective, wasteful and can easily leach in to dams and waterways.
- Phosphorus: the first sign of phosphorus deficiency is a deep green appearance of plants and a reduction in leaf size. As the deficiency becomes more severe the upper surface of leaves develops a dark metallic sheen, while the underside becomes reddish purple (Figure 52).
Figure 56 - Phosphorus deficiency on leaf.
The fruit and flowers tend to be smaller than normal and the roots are less abundant, stunted and darker.
Most phosphorus should be applied before planting and placed within the root zone. Applying superphosphate after laying plastic mulch in either the planting holes or in the walkways is not effective. Soluble phosphorus fertiliser can be apllied by fertigation.
- Potassium: the symtoms of potassium deficiency can be easily confused with those of magnesium deficiency, or with leaf scorch caused by salinity, wind, sun or dry conditions. Mature leaves show a browning and drying of the upper leaf surface, progressing from the margin to the centre of the leaf between the veins. At the same time the mid-rib section of the leaf becomes dry and darker. These symptoms first appear on lower leaves (Figure 53).
Figure 57 - Potassium deficiency with increasing severity with age.
Apply potassium before planting and during early fruit development. A higher rate of potassium should be used in sandy soils and in high rainfall areas. Apply soluble potassium by fertigation after planting.
- Magnesium: marginal leaf scorch begins as yellowing and browning of the upper leaf margin, progressing towards the centre of the leaf between the veins (Figure 54).
The basal part of the leaf and the short petiole remain green and turgid, unlike in potassium deficiency. Fruit from magnesium deficient plants appears normal, except that they are a lighter colour and softer in texture.
To control this physiopatology apply dolomite several months before planting if soil test results indicate low levels of magnesium and low pH. Apply magnesium sulfate (epsom salts) by fertigation at first signs of deficiency and repeat if needed.
Figure 58 - Magnesium deficiency. Marginal scorch (left) and normal leaf (right).
A foliar spray of magnesium sulfate can also be used to give immediate relief, but it should be tested on a few plants first. Discontinue at the first sign of phytotoxicity.
The heavy use of potassium fertilisers can reduce the uptake of magnesium by plants.
- Calcium: during rapid leaf growth "tip burn" symptoms may appear on immature leaves.The tips of these leaves fail to expand fully and become black. Fruit develop a dense cover of seeds, either in patches or over the entire fruit, and develop a hard texture and acid taste (Figure 55). The roots become short, stubby and dark.
Figure 59 - Calcium deficiency. Leaf tip burn (left) and small fruit with dense cover of seeds (left). Normal fruit (right). (right).
To control this physiopathology adjust the soil pH. Apply calcium in the form of agricultural lime or dolomite before planting. Apply calcium nitrate by fertigation or as foliar spray at first sign of deficiency.
- Zinc: it is uncommon in New South Wales. It is easily distinguished by the green halo that develops along the serrated margins of young, immature leaf blades.
As the leaves continue to grow the blades become narrow at the base and eventually become elongated with severe deficiency. Yellowing and green-veining occurs (Figure 56).
Figure 60 - Zinc deficiency on leaves.
The fruit size may appear normal, although the number of fruit is reduced.
Add zinc sulfate or chelate to the fertliser program and apply at planting to soils known to be low in zinc.
The application of zinc as a foliar spray or by fertigation can give immediate relief. However, the use of zinc sulfate as a foliar spray may damage young leaves, flowers and fruit. Discontinue treatment at the first sign of phytotoxicity.
- Boron: younger leaves show puckering and tip-burn, followed by marginal yellowing and crinkling with reduced growth at the growing point (Figure 57, left), while the fruits resulting in small, "bumpy", and of poor quality (Figure 57, right).
Figure 61 - Boron deficiency on leaves (left) and on the fruit (right).
Moderate deficiency of boron reduces the flower size and decreases pollen production, resulting in small, "bumpy" fruit of poor quality. Root growth can be stunted.
Controlling this physiopathology apply a foliar spray of boron or add borax to the soil before planting. Boron is toxic to plants and should not be used excessively.
- Iron: iron is essential for many plant functions. Some of them are:
Chlorophyll development and function.
It plays a role in energy transfer within the plant.
It is a constituent of certain enzymes and proteins.
Iron functions in plant respiration, and plant metabolism.
It is involved in nitrogen fixation.
Yellowing and green veining are the first signs of iron deficiency. As the deficiency becomes more severe, yellowing increases to a point of bleaching and the leaf blades turn brown (Figure 58).
Figure 62 - Iron deficiency on leaves.
Fruit size and quality are not greatly affected.
Alkaline or poorly drained soils can induce iron deficiency. Check soil pH levels. If the pH level is high, cease liming and use acid-forming fertilisers such as sulfate of ammonia.
To control iron deficiency apply iron sulfate by fertigation when symptoms first appear. Foliar sprays with iron sulfate or chelate can also be used.
To avoid the deficiencies of nutrients or their quick check must be able to apply fertigation or foliar sprays. Therefore, we must know the solubility of the fertilizer (Table 7) and the standards of the foliar analysis (Table 8).
The prinples of the tissue analysis are:
- Optimal level of nutrients at a certain time of year have been established through research.
- Collect plant tissue at this same time of year to determine if plant has sufficient nutrients in the tissue (leaves).
- Use this information to inform nutrient management decisions.
| Table 7 Soluble fertilisers suitable for fertigation in strawberries.
|| Application rate
|Early flowering onwards
|Improve fruit size. Reduce at fruiting. Stop if fruit is soft.
|Early flowering onwards
|Improve fruit size. Stop if fruit is soft.
|Sulfate of ammonia:
|21% N + 24% S
|Early flowering onwards
|Corrosive to mild steel.
|15.5% N + 12% Ca
|Post flowering and fruit development
|Improve fruit colour and firmness. Do not mix with magnesium sulfate.
|13% N + 38% K
|Flowering and fruiting
|Assist in maintaining fruit quality and flavour.
|40% K + 16% S
|Assist in maintaining fruit quality and flavour.
|22% P + 12.5% N
|Early in season and after cutting back for second crop
|Improve flower and fruit size. Improve root growth. Apply before cutting back if plants are kept for a second year.
|10% Mg + 14% S
|Improve fruit colour and firmness. Do not mix with calcium nitrate.
| Table 8 Sufficiency ranges for strawberries.
|| Deficient Below
- Soil quality: poor soil conditions can cause poor growth and plant death during the establishment year. Very high soil acidity levels can contribute to poor growth. Strawberries are shallow rooted, and have a low tolerance to salts. Winter drainage will help leach salts from the soil. Irrigation water should be tested for dissolved salts, and plants should be irrigated during the summer months to keep the salts below the root zone. Salt injury can occur in south-western BC but is very site-specific and is not a problem in most of Canada.
Soil quality is the measure of a soils health and its ability to resist erosion, compaction, and other stresses, while maintaining economic productivity. Assessing the soil quality for each field and taking steps to maintain or improve it will ensure continued productivity. It is important to keep in mind that soil and its management are part of the overall crop production system.
The main parameters, the study of which can identify the quality of the soil on which to grow strawberry, are as follows:
- Compaction and soil diagnostics. Crops grown in compacted soils often have a restricted root system (Figure 63, a). This leads to poor nutrient uptake, stunted growth, a general lack of vigour, and reduced yields. Compaction affected plants are also more susceptible to disease and insect pressure.
The root systems of affected plants often show signs of a physical barrier. The root tips may become stunted and club-like, or the plant may produce a proliferation of horizontal secondary roots, in an attempt to outgrow the compaction. Transplanted crops grown on compacted soils often fail to leave the root plug, or they may develop a corkscrew-shaped taproot.
Compaction may be assessed using several inexpensive tools, such as a tile probe, plot flags or a shovel. Take note of any resistance or barriers when probing the soil and assess the depth at which the resistance is felt. Consider soil moisture levels when probing. Soil strength increases as soils dry out, consequently a dry soil will exhibit more resistance than a very wet soil. Assessments of potential soil compaction should be performed on moist soils.
The types of compaction are (figure 63):
Soil is the basis of farming. The goal of soil management is to protect soil and enhance its performance, so you can farm profitably and preserve environmental quality for decades to come:
- Crusting is common on soils with poor structure and low aggregate stability. Moderate to intense rain events after planting shatter the soil aggregates causing the finer textured particles to bind together and fill any open pores on the soil surface. As the soil dries, a thick and impermeable crust forms. Soils with a heavy crust will often exhibit poor crop emergence and increased seed decay and root rots. Excessive secondary tillage during seedbed preparation makes soils more prone to crusting. Crusting is more commonly found on soils with a finer texture (i.e. loams to clays).
- Sidewall Compaction is caused when planting activities take place on wet soils. The planters disk openers cause the soil to smear, effectively sealing it, limiting both root growth and nutrient uptake. The emerging plants will often exhibit flattened roots and may have a proliferation of secondary roots growing horizontally along the planter trench. Under moist soil conditions the growing crop may be able to grow past the barrier. Sidewall compaction is more commonly found on soil types with high proportions of silt and clay.
- Plow Pans are hard, compacted layers occurring 15- 30 cm (6- 12 in.) below the soil surface. Wet harvest seasons and long-term intensive vegetable crop-oriented rotations can result in the formation of a plow pan. The effects of a plow pan are most obvious in extremely wet or extremely dry years. In wet years, the compacted zone may cause drainage problems and waterlogged soils. In dry years, the compaction-confined root system is unable to access soil water below the plow pan. Plow pans and tillage pans can be found on any soil type including coarse sands and sandy loams.
- Rotation with deep rooted crops, such as corn or alfalfa, or fibrous rooted crops, such as wheat will help to loosen compacted soils. They will also improve the soil structure, making it less susceptible to compaction in the future.
- If possible, avoid working in wet fields, particularly with heavy equipment. The carrying capacity of dry soil is much greater than that of moist soil. Ensure tillage operations are performed when the soil is at proper moisture conditions at the tillage depth. Alternate tillage depth so that tillage pans are not created.
- Use radials, large tires or tracks that create a long narrow footprint to restrict compaction. Reduce the tire pressure to reduce the force on the surface of the soil. This will only be effective with radial tires. The tires must be large enough to carry the equipment at reduced pressures. Check with the manufacturer to confirm that the tires are rated to operate at low pressures.
- Avoid high axle loading, which will cause compaction in the subsoil, even with low tire pressure. Keep equipment weight and loads as low as practical (below 4.5 tonnes/axle or 5 tons/axle). Limit traffic with heavy equipment to laneways or harvest rows rather than tracking the entire field.
Figure 63 - Effects of soil compaction on roots (a). Tire ruts and compaction (b).
- Drainage: drainage patterns in the field have a big impact on crop growth and pest susceptibility. Poorly drained areas of the field are often more prone to diseases such as Phytophthora, damping-off and root rots.
Water drains through the soil through large pores, cracks and earthworm channels. Drainage is influenced by several factors including: topography, soil texture, soil structure, compaction, tillage and even buried layers of crop residues (Figure 64, a). The texture of the sub-soil layers can play a large role in soil drainage. For example, a coarse sandy-loam soil with a clay sub-soil may experience slow drainage and waterlogged conditions, despite its surface texture.
Crops may appear yellow or dead in waterlogged areas. Crop growth may be stunted and plants may be more susceptible to disease. Plants grown in wet soils often have unusually shallow root systems (Figure 64, b).
Use a soil probe or auger to look at the full soil profile and feel the soil at various depths. Look for changes in soil texture and moisture with depth. Soil colour and the colour patterns are good indicators of natural drainage characteristics. Well-aerated or well-drained soils are usually red, yellow or brown in colour. Grey or blue soils indicate a that it has been saturated for extended periods of time and is usually poorly drained. Mottled areas (orange or red streaks on a dull background) indicate soils that are saturated or nearly saturated for shorter periods of time (usually seasonal variations) so these are imperfectly drained.
For groped to solve problems elativi drainage:
- Consider the cause of the poor drainage, some factors like soil texture can not be changed.
- Tile drains, grassed waterways and other types of surface drains, can help improve internal drainage.
- Drainage can also be improved through good crop rotation. Rotate between a variety of crops with different types of root systems.
- Additions of organic amendments like manure and compost can help to build better soil structure, improving the network of macropores.
- Timely and reduced tillage can also aid in the building of soil structure.
Figure 64 - Water ponding in field (a). Water ponding in strawberry field (b).
- Erosion: almost every farm has felt the effect of some form of erosion over the years. This can have long term impacts on soil productivity. Erosion moves not only soil; it also moves and redistributes organic matter, fertilizers and pesticides. The soil erosion it caused by water and by Wind.
Water erosion may not actually remove soil from a field but it can significantly rearrange soil within a field. It increases the variability of the soil and the crop growth within a field. Water erosion creates rills or small gullies in the field. It is most common early in the season on bare soils or when the crop canopy is not yet fully developed. Eroded areas tend to display a lighter soil colour and poor soil structure. Knolls and side hills are most prone to erosion. Crops grown on eroded soils often display poor emergence, experience delayed establishment and exhibit poor growth compared with the rest of the field. Eroded knolls tend to have a lower pH, further contributing to poor crop growth. Soil in low spots, or areas where the eroded soil is deposited, is usually darker in colour than the rest of the field. Use a soil probe to examine and compare topsoil depth in various parts of the field.
Wind erosion is a common problem on many of the coarse textured, low organic matter soils used for vegetable production. Wind erosion in the early spring may expose or remove seeds in one area of the field while deeply burying them in another. Wind blown soil can damage or kill young plants and wounds caused by blasting sand often act as a point of entry for foliar diseases. Crops are most susceptible to wind damage early in the season before the canopy is established.
Wind erosion moves soil in three ways:
Crop residues and cover crops keep the soil covered and slow the movement of wind and water across the field. Cover crop roots also anchor the soil, preventing its movement.
- Suspension occurs when very fine soil particles are carried high into the air. While highly visible, this accounts for a very small amount of the total soil lost by wind.
- Saltation is the most damaging, accounting for more than 50% of the soil movement usually. It occurs when fine to medium sized soil particles are lifted a short distance into the air and drop back to the soil surface where the particles can damage crops and dislodge more soil.
- Creep is a more gentle movement. Larger soil particles are dislodged and roll along the soil surface. This accounts for about 25% of soil movement by wind. Creep gives the soil surface the appearance of wave action or mini dune formation.
Rotate vegetable crops with cereals or other crops that leave high amounts of residue. Use erosion control structures such as grassed waterways, tile drains and water and sediment control basins. Tree windbreaks and grassy wind strips slow the movement of wind and protect the adjacent crop.
Aggregate stability is an important parameter whose knowledge contributes to the prevention of erosion serve as early indicators of recovery or degradation of soils. Soil aggregates are groups of soil particles that bind to each other more strongly than to adjacent particles. Aggregate stability refers to the ability of soil aggregates to resist disintegration when disruptive forces associated with tillage and water or wind erosion are applied. Wet aggregate stability suggests how well a soil can resist raindrop impact and water erosion, while size distribution of dry aggregates can be used to predict resistance to abrasion and wind erosion.
Changes in aggregate stability may serve as early indicators of recovery or degradation of soils. Aggregate stability is an indicator of organic matter content, biological activity, and nutrient cycling in soil. Generally, the particles in small aggregates (< 0.25 mm) are bound by older and more stable forms of organic matter. Microbial decomposition of fresh organic matter releases products (that are less stable) that bind small aggregates into large aggregates (> 2-5 mm). These large aggregates are more sensitive to management effects on organic matter, serving as a better indicator of changes in soil quality. Greater amounts of stable aggregates suggest better soil quality. When the proportion of large to small aggregates increases, soil quality generally increases. Stable aggregates can also provide a large range in pore space, including small pores within and large pores between aggregates. Pore space is essential for air and water entry into soil, and for air, water, nutrient, and biota movement within soil. Large pores associated with large, stable aggregates favor high infiltration rates and appropriate aeration for plant growth. Pore space also provides zones of weakness for root growth and penetration. Surface crusts and filled pores occur in weakly aggregated soils. Surface crusts prevent infiltration and promote erosion; filled pores lower water-holding and air-exchange capacity and increase bulk density, diminishing the conditions for root growth. Specific problems that might be caused by poor function: Aggregate stability is critical for infiltration, root growth, and resistance to water and wind erosion. Unstable aggregates disintegrate during rainstorms. Dispersed soil particles fill surface pores and a hard physical crust can develop when the soil dries. Infiltration is reduced, which can result in increased runoff and water erosion, and reduced water available in the soil for plant growth. A physical crust can also restrict seedling emergence.
Wind normally detaches only loosely held particles on the soil surface, but as blowing soil particles are accelerated by the wind they hit bare soil with sufficient energy to break additional particles loose from weakly aggregated soil. This action increases the number of particles that can be picked up by the wind and abrade a physically-unprotected soil surface.
Practices that lead to poor aggregate stability include:
a) Tillage methods and soil disturbance activities that breakdown plant organic matter, prevent accumulation of soil organic matter, and disrupt existing aggregates.
b) Cropping, grazing, or other production systems that leave soil bare and expose it to the physical impact of raindrops or wind-blown soil particles.
c) Removing sources of organic matter and surface roughness by burning, harvesting or otherwise removing crop residues.
d) Using pesticides harmful to beneficial soil microorganisms.
It is possible improve the aggregate stability of your soil by increasing levels of organic matter or applying specialized chemical compounds, such as anionic polyacrylamide (PAM). Practices that keep soil covered physically protect it from erosive forces that disrupt aggregation, while also building organic matter. Any practice that increases soil organic matter, and consequently biological activity, improves aggregate stability. However, it can take several growing seasons or years for significant organic matter gains. In contrast, management activities that disturb soil and leave it bare can result in a rapid decline in soil organic matter, biological activity, and aggregate stability.
Aggregates form readily in soil receiving organic amendments, such as manure. They also form readily where cover and green manure crops and pasture and forage crops are grown, and where residue management and/or reduced tillage methods are used.
Improving aggregate stability on cropland typically involves cover and green manure crops, residue management, sod-based rotations, and decreased tillage and soil disturbance. Aggregate stability declines rapidly in soil planted to a clean-tilled crop.
Pasture and forage plants have dense, fibrous root systems that contribute organic matter and encourage microbial activity. However, grazing and fertility must be managed to maintain stands and prevent development of bare areas or sparse vegetation.
Conservation practices resulting in aggregate stability favorable to soil function include:
- Conservation crop rotation.
- Cover crop.
- Pest management.
- Prescribed grazing.
- Residue and tillage management.
- Salinity and sodic Soil management.
- Surface roughening.
- Soil texture: soil particles come in three main size categories; sand, silt and clay. Knowledge of soil texture can be important when diagnosing issues such as drought stress, compaction and certain crop diseases, such as root rots and Fusarium. It can also be used to help schedule irrigation.
Hand texturing is the most common way to determine soil texture. A particle size analysis will give a complete breakdown of soil texture. This lab test is fairly expensive, but the information can be used to calculate the water holding capacity of a soil for irrigation scheduling. Soil texture in most fields is highly variable. It also changes dramatically within the soil profile. When assessing soil-texture related problems, such as drainage, it is valuable to identify the soil texture at depths below the plow layer.
A shovel, soil probe or soil auger will give easy access to the soil profile for texturing
- Soil structure: Soil structure refers to how the soil particles (sand, silt and clay) are arranged into clumps or aggregates. Soil aggregates are bound together by clay, organic matter and root exudates. Soil structure has a significant effect on crop establishment, growth and productivity.
Soil structure influences:
The structure of a soil is influenced by soil texture; climate; biological activity; and farm management practices, including tillage, crop rotation and machinery/equipment use patterns. Soils are often described as structureless, spheroidal, blocky or platy:
- the movement of water into and through soil;
- the degree of aeration;
- the ability of crop roots to grow through the soil profile;
- the ability of the soil to resist soil erosion.
Soil structure can be improved through a variety of management techniques including: crop rotations involving cereals and forages; the use of cover crops; the addition of organic matter sources like manure and compost; and reduced tillage. Be aware of the number of traffic passes, axle loading, harvest travel patterns and the depth of tillage.
- Structureless soils have no observable aggregation and no definite arrangement of the soil particles. Sands and sandy-loam soils are often structureless with a single grain arrangement of the soil particles. Clay soils may also be described as structureless when the particles form a massive structure with no small aggregates within. This is more commonly seen in finer textured soils like clays, particularly when they have been worked wet or exposed to heavy loads under wet conditions.
- Spheroidal soils have a granular structure. The aggregates are 1- 10 mm (1/25- 2/5 in.) in diameter with rounded corners. This structure is usually seen in the A horizon or the upper layer of fine or medium-textured soils. Granular structure in the seed or transplant zone is important for good contact and early establishment.
- Blocky soil aggregates are often larger in size (5- 50 mm or 1/5- 2 in. in diameter) and form irregular-shaped or cube-like blocks. This structure promotes good drainage, aeration and root penetration. Usually these structures are found in the B horizon or just below the colour change in many soils. Blocky structures greater than 50 mm (2 in.) in diameter are often an indication of compaction or soil management problems.
- Platy soils form thin layers or horizontal planes. This type of structure can be found in both surface and subsurface soil horizons. It is commonly seen in undisturbed or no-till soils. Platy structures in sandy soils often indicate compaction problems.
- Soil pH: pH is a measure of the level of acidity or alkalinity in the soil. The pH scale ranges from 0 to 14 and reflects the hydrogen ion concentration in the soil. A pH value of 7.0 is neutral. Values below 7.0 are acidic; those above 7.0 are alkaline or basic.
Soil pH has an impact on the availability of most nutrients. Elements such as nitrogen, calcium and molybdenum are less available at pH levels below 6.0. The availability of other nutrients, such as manganese, zinc, phosphorus and potassium decreases at pH levels greater than 7.0.
Vegetables grown on mineral soils have a target pH of 6.1 to 6.5. On muck soils the target pH is 5.1 to 5.5.
pH also affects the activity of soil micro-organisms. These organisms build soil structure, cycle organic matter or fix nitrogen in legume nodules.
Soil pH can have a drastic effect on the performance and breakdown of some pesticides. The efficacy of soil applied triazine herbicides like atrazine and metribuzin is often decreased on acidic soils. pH may also affect the breakdown of residual herbicides used in field crops. Imazethapyr, flumetsulam and cloransulam degrade very slowly at a soil pH less than 6.0 to 6.5, potentially causing problems with vegetable crops grown after crops treated with these products. Chlorimuron-ethyl degrades slowly at a pH greater than 7.
Soil testing is the only reliable way to determine whether the soil pH needs adjusting. However some areas of a field may show symptoms of low pH even though the average pH or even the grid sampled pH for the entire field may be acceptable.
Sandy knolls often have a lower pH than the rest of the field. These areas should be sampled separately.
A very low pH can cause some crop roots to appear stunted and burnt. Plant establishment in low pH areas may be poor, or the crop may appear stunted and delayed. Crops such as barley and peas are very sensitive to low pH.
Plant species differ in their requirement and tolerance of different pH levels in soil. The buffer pH is used to calculate the amount of liming material based upon the ability of the soil to resist changes in pH. Lime will not change soil pH overnight. Agricultural limestone does not dissolve quickly. The full effects of liming may take up to 3 years. It is important to ensure that lime is applied well in advance of sensitive crops being grown.
- Tools for Soil Diagnostics:
- Hands: dont overlook the value of a hands-on approach to diagnosing soil problems. Use the hand texturing chart to estimate the soil texture at the surface or throughout the depth of the soil profile.
- Knife: keep a separate knife for soil diagnostics as soil will rapidly dull the edge on any blade. Knives can be used to assess soil density or compaction. They can be used to probe the soil, find seeds and estimate planting or tillage depth. They are also used to gage the severity of a soil crust.
- soil probe: the soil probe is a highly versatile tool (Figure 65). It can be used to take soil samples for nutrient analysis. Standard soil samples are taken to a depth of 15 cm while soil nitrate samples are taken to 30 cm (1 ft.). Insert the probe straight into the soil to ensure an accurate depth of core. A probe can also be used to check the full soil profile for soil moisture, resistance or compacted layers. Inspect the soil core for colour and textural changes through the profile. Avoid soil probes with foot pedals. While the pedal assists with insertion, it also prevents the use of the probe for deeper profile sampling.
Figure 65 - Soil probe used to take soil samples.
- Soil Auger or Dutch Auger: soil augers are available in a variety of diameters. Similar to the soil probe, an auger can be used to examine the soil profile with minimal disturbance. The curved blade is particularly useful for sampling in dry, stony or coarse textured soils. Augers allow the gathering of samples for nutrient or chemical testing, soil moisture or to assess texture and colour at depth.
- Tile Probe: a tile probe is a straight, slightly flexible, steel rod approximately 1 to 1 1/2 metres (3- 5 ft.) in length with a cross bar handle to allow for insertion and removal from the soil. The rod has a sharp, cone-shaped tip, with a diameter slightly greater than the rod to allow for easy insertion and minimal soil friction. Tile probes can be used to locate tile or to locate compacted soil layers. Use the tile probe to test the suspected area to a depth of 50 cm and compare to a fencerow or unaffected area. Insert the tile probe into the ground at a slow and steady pace. Keep your arms slightly bent. They act as the pressure gauge feeling the force required to push the tip through the soil. Record the depths at which the tip of the probe meets resistance. Keep in mind that soil moisture plays a large part in soil strength a dry soil will resist penetration more than a wet soil regardless of soil compaction.
- Marking Flags can be used to assess compaction. Insert the wire gently and smoothly until the wire starts to bend. Measuring compaction in several areas across the field may help to identify patterns and possible causes of the compaction.
- Shovels and hand trowels can be used to gather soil samples, check soil moisture and assess soil structure. Dig up and compare the roots of both healthy and unhealthy plants to assess possible soil related, disease or insect problems affecting the crop's growth.
Delicious, rich-red, sweet, yet gently tart strawberries are among the most popular berries.
Strawberry is a small, low-lying, spreading shrub. It bears small white flowers which eventually develop into small conical, light green, immature fruits. They turn red upon maturity with each berry featuring red pulp with tiny, yellow color seeds piercing through its surface from inside. Its top end carry a green leafy cap and stem that is adorning its crown.
Each berry features conical shape, weighs about 25 grams and measures about 3 cm in diameter. The berries have the taste that varies by cultivar, and ranges from quite sweet to acidic.
Table 9 shows the percentage composition of the fruits of strawberry.
| Tabella 9 Analysis of nutrients of strawberry: nutrition value per 100 g.
Total Fat (g)
Dietary Fiber (g)
Pantothenic acid (mg)
Vitamin A (IU)
Vitamin C (mg)
Vitamin E (mg)
Vitamin K (µg)
There are numerous health benefits of strawberries:
- Strawberry is low in calories (27 cal/100 g) and fats but rich source of health promoting phyto-nutrients, minerals, and vitamins that are essential for optimum health.
- Strawberries have significantly high amounts of phenolic flavonoid phyto-chemicals called anthocyanins and ellagic acid. Scientific studies show that consumption of these berries may have potential health benefits against cancer, aging, inflammation and neurological diseases.
- Strawberry has an ORAC value (oxygen radical absorbance capacity, a measure of anti-oxidant strength) of about 3577µmol TE per 100 grams.
- Fresh berries are an excellent source of vitamin-C (100 g provide 58.8 mg or about 98% of RDI), which is also a powerful natural antioxidant. Consumption of fruits rich in vitamin C helps the body develop resistance against infectious agents, counter inflammation and scavenge harmful free radicals.
- The fruit is rich in B-complex group of vitamins. It contains very good amounts of vitamin B-6, niacin, riboflavin, pantothenic acid and folic acid. These vitamins are acting as co-factors help the body metabolize carbohydrate, proteins and fats.
- Strawberries contain vitamin A, vitamin E and health promoting flavonoid poly phenolic antioxidants such as lutein, zea-xanthin, and beta-carotene in small amounts. These compounds help act as protective scavengers against oxygen-derived free radicals and reactive oxygen species (ROS) that play a role in aging and various disease processes.
- Furthermore, they contain good amount of minerals like potassium, manganese, fluorine, copper, iron and iodine. Potassium is an important component of cell and body fluids that helps controlling heart rate and blood pressure. Manganese is used by the body as a co-factor for the antioxidant enzyme, superoxide dismutase. Copper is required in the production of red blood cells. Iron is required for red blood cell formation. Fluoride is a component of bones and teeth and is important for prevention of dental caries.
Blood sugar benefits. One of the more recent areas of health benefit to be documented in strawberry research is the area of blood sugar benefits. Several recent studies have found regular intake of strawberries to be associated with decreased risk of type 2 diabetes. In some of these studies, frequency of strawberry intake definitely seems to matter since an intake frequency of once per week or less is not associated with blood sugar benefits in some studies. In these studies, significant benefits do not emerge until frequency of intake reaches at least 2-3 strawberry servings per week.
Of special interest for blood sugar regulation is the relationship recently documented by researchers between intake of strawberries, intake of table sugar, and resulting blood sugar levels. As you might expect, excess intake of table sugar (in a serving size of 5-6 teaspoons) was able to produce an unwanted blood sugar spike in study participants during this study. But as you might not expect, this blood sugar spike was actually reduced by simultaneous consumption of strawberries. Approximately one cup of fresh strawberries (approximately 150 grams) was able to decrease blood sugar elevations when table sugar was consumed along with strawberries. The investigators speculated that polyphenols in strawberries played a major role in helping regulate blood sugar response. One particular type of polyphenol in strawberriesellagitanninsmight have been especially important for this blood sugar-relating benefit. Ellaginannins are polyphenols that are known to inhibit the activity of an enzyme called alpha-amylase. Since this enzyme is responsible for breaking amylose starches into simple sugars, fewer simple sugars might be released into the blood stream when activity of this enzyme is reduced.
Anti-cancer benefits. Since chronic, excessive inflammation and chronic, excessive oxidative stress (lack of antioxidant nutrients and unsupported oxygen metabolism) are often primary factors in the development of cancer, strawberries would definitely be expected to have cancer risk-lowering properties given their outstanding antioxidant and anti-inflammatory nutrient content. Anti-cancer benefits from strawberries are best documented in the case of breast, cervical, colon, and esophageal cancer. Most of the tumor-inhibiting studies on animals have focused on the phytonutrient content of strawberries. Among the strawberry phytonutrients, ellagic acid and ellagitannins in strawberry have emerged as anti-cancer substances of special interest. While the anti-cancer (chemopreventive) properties of these phytonutrients have yet to be fully understood, their ability to lower risk for some forms of cancer may be related to their ability to boost the activity of antioxidant enzymes like catalase or superoxide dismustase, their ability to lessen the activity of pro-inflammatory enzymes like cyclo-oxygenase 2 (COX-2), or their ability to lessen expression of the enzyme inducible nitric oxide synthase (iNOS). Whatever the mechanism or combination of mechanisms, strawberries are likely to bring anti-cancer health benefits to your diet.
Other health benefits. A growing area of health research on strawberries is the area of aging and aging-related events. Several preliminary studies on intake of strawberries on aged animals has shown enhanced cognitive function (in the form of better object recognition) following ingestion of a diet with 2% of the calories provided by strawberry extracts. Enhanced motor function (in the form of better balance and coordination of movements) has also been shown in these strawberry extract studies. Some of the strawberry impact in these aging studies has been attributed to the ability of strawberry phytonutrients to lower the presence of pro-inflammatory messaging molecules like nuclear factor kappa-B.
Improvement of inflammatory bowel problemsincluding ulcerative colitis and Crohn's diseasehas also been demonstrated in preliminary studies on animals with daily strawberry extract or strawberry powder intake. Interestingly, even though strawberries contain relatively small amounts of salicylic acid (an anti-inflammatory compound very similar to the acetylsalicylic acid of aspirin), some researchers have suggested that this naturally-occurring anti-inflammatory substance in strawberries might be partly responsible for decreased inflammation in the digestive tract of individuals diagnosed with inflammatory bowel diseases like ulcerative colitis or Crohn's disease.
Inflammation-related arthritis (including rheumatoid arthritis), and inflammation-related diseases of the eye (including macular degeneration) are two additional areas in which strawberries may turn out to provide important health benefits. Even though health research in these areas is in a preliminary stage, the unique combination of anti-inflammatory phytonutrients in strawberries is likely to explain some of the key potential benefits in these areas.
Antioxidant and anti-inflammatory phytonutrients in strawberries are listed below (* indicates that these are typically in small or trace amounts)
- Hydroxy-benzoic acids
- ellagic acid
- gallic acid
- vanillic acid*
- salicylic acid
- Hydroxy-cinnamic acids
- cinnamic acid
- coumaric acid
- caffeic acid
- ferulic acid
Several research studies have shown that these diverse strawberry phytonutrients actually work together in synergistic fashion to provide their cardiovascular benefits. Decreased oxidation of fats (lipid peroxidation) in the cell membranes of cells that line our blood vessels; decreased levels of circulating fats, including total cholesterol and LDL cholesterol; and decreased activity of angiotensin I-converting enzyme (ACE), an enzyme whose overactivity increases our risk of high blood pressure are results that have all been documented following daily intake of strawberries over 1-3 months period of time. Amounts of strawberries in most studies were equivalent to 1-2 cups of strawberries per day.
Some substances such as essential oils, tannins and flavones which give the fruit color and scent characteristic have high antioxidant power.
The quantitative content of these substances varies greatly depending on the variety, growing conditions, the degree of maturation, the time and mode storage after harvest. Obviously in the fresh fruit with the right degree of maturation observed the optimal amounts of polyphenolic compounds.
Several scientific experiments thus confirm that the strawberry, as all fruit and vegetables, contains protective factors, mostly vitamins and polyphenolic compounds. The first are nutrients essential for the proper functioning of the metabolism, the latter are substances of various kinds that play an antioxidant and protective neutralizing the formation and/or proliferation of free radicals.
Strawberries can be available year-round in the stores but are fresh and plentiful from spring through mid-summer.
In the stores, choose berries that feature deep red with attached green caps, plump, shiny, free of sand and mold. Avoid those appear dull, sunken or flattened and those with signs of mold, cuts or discolored patches on the surface. Unripe berries have green or yellow patches on their surface. Since the berries cease ripening soon after their harvest, unripe berries should be avoided as they are likely to be sour and of inferior in quality. They perish early and therefore, should only be purchased a few days prior to use.
Before storing inside the refrigerator, sort out any damaged and those affected by mold so that they should not spoil healthy ones. Place them in a wide bowl or spread out on a plate covered with a paper towel. They keep fresh inside the refrigerator for a day or two. Use them as early as possible. For extended storage, place them in the freezer compartment.
As strawberries are very perishable, they should only be purchased a few days prior to use. Choose berries that are firm, plump, free of mold, and which have a shiny, deep red color and attached green caps. Since strawberries, once picked, do not ripen further, avoid those that are dull in color or have green or yellow patches since they are likely to be sour and of inferior quality. Full ripe berries will not only have the peak flavor and texture, but will have more nutrients. "Full ripe" in this case means optimally ripe, not overripe. Both underripe and overripe strawberries have been show to have lower vitamin C content and decreased phytonutrient content in comparison to optimally ripe strawberries.
We believe that the surprisingly fragile and perishable nature of strawberries is especially important,
Food scientists have recently taken a close look at storage time, storage temperature, storage humidity, and degree of strawberry ripeness and found significant differences among their impact upon nutrient retention. On average, studies show 2 days as the maximal time for strawberry storage without major loss of vitamin C and polyphenol antioxidants. It's not that strawberries become dangerous to eat or invaluable after 2 days. It's just that more storage time brings along with it substantially more nutrient loss. In terms of humidity, 90-95% has been shown to be optimal. Most refrigerators will average a much lower humidity (between 80-90%). Because air circulation inside the fridge can lower humidity, you may want to give your strawberries more storage humidity by putting them in your refrigerator's cold storage bins (if available). Those cold storage bins will help boost humidity by reducing air circulation. If your refrigerator does not have storage bins, you can use a sealed container for refrigerator storage of your strawberries. Optimal temperature for strawberry storage over a 2-day period has been found to be relatively cold 2 °C. All public health organizations recommend refrigerator temperatures of 4.4 °C as the maximum safe level for food storage.
However, if you are storing sizable amounts of fruits and vegetablesincluding strawberries in your refrigerator, you may want to consider setting your refrigerator to a lower-than-maximum temperature setting in the range of 2-3 °C).
Medium-sized strawberries are often more flavorful than those that are excessively large. If you are buying strawberries prepackaged in a container, make sure that they are not packed too tightly (which may cause them to become crushed and damaged) and that the container has no signs of stains or moisture, indication of possible spoilage. Strawberries are usually available year round, although in greatest abundance from the spring through the mid-summer.
The very fragile nature of strawberries means that great care should be taken in their handling and storage. Before storing in the refrigerator, remove any strawberries that are molded or damaged so that they will not contaminate others. Place the unwashed and unhulled berries in a sealed container to prevent unnecessary loss of humidity. Strawberries will maintain excellent nutrient content if properly stored in a refrigerator for two days. Make sure not to leave strawberries at room temperature or exposed to sunlight for too long, as this will cause them to spoil.
To freeze strawberries, first gently wash them and pat them dry. You can either remove the cap and stem or leave them intact, depending upon what you will do with them once they are thawed. Arrange them in a single layer on a flat pan or cookie sheet and place them in the freezer. Once frozen, transfer the berries to a heavy plastic bag and return them to the freezer where they will keep for up to one year. Adding a bit of lemon juice to the berries will help to preserve their color. While strawberries can be frozen whole, cut or crushed, they will retain a higher level of their vitamin C content if left whole.
Commercial food processing can dramatically lower the nutrient content of strawberries, especially their phytonutrient content. For example, we've seen several studies showing very little retention of certain anthocyanin phytonutrients in baby foods made from strawberries or other brightly-colored berries. The dramatic impact of some processing methods may be to do heat, pH (changes in acidity during processing), oxygen exposure, light exposure, the physical and mechanical impact of processing, or a combination of these factors. In any case, a much safer bet in terms of strawberries and nourishment is to stick with fresh berries or carefully frozen berries, and in the case of baby food or the feeding of young children, to purée the berries in a blender so that overall processing is kept to a minimum.
There are also personal contraindications for those who want to use the strawberry fruit, especially if you abuse its use in food. Remember that for the cultivation of strawberries may need to resort to the use of pesticides and that oxalic acid is present in the fruit.
Strawberries and pesticide residues. Virtually all municipal drinking water in the United States contains pesticide residues, and with the exception of organic foods, so do the majority of foods in the U.S. food supply. Even though pesticides are present in food at very small trace levels, their negative impact on health is well documented. The liver's ability to process other toxins, the cells' ability to produce energy, and the nerves' ability to send messages can all be compromised by pesticide exposure. According to the Environmental Working Group's 2014 report "Shopper's Guide to Pesticides," conventionally grown strawberries are among the top 12 fruits and vegetables on which pesticide residues have been most frequently found. Therefore, individuals wanting to avoid pesticide-associated health risks may want to avoid consumption of strawberries unless they are grown organically.
Strawberries and oxalates. Strawberries are among a small number of foods that contain measurable amounts of oxalates, naturally-occurring substances found in plants, animals, and human beings. When oxalates become too concentrated in body fluids, they can crystallize and cause health problems. For this reason, individuals with already existing and untreated kidney or gallbladder problems may want to avoid eating strawberries. Laboratory studies have shown that oxalates may also interfere with absorption of calcium from the body. Yet, in every peer-reviewed research study we've seen, the ability of oxalates to lower calcium absorption is relatively small and definitely does not outweigh the ability of oxalate-containing foods to contribute calcium to the meal plan. If your digestive tract is healthy, and you do a good job of chewing and relaxing while you enjoy your meals, you will get significant benefitsincluding absorption of calciumfrom calcium-rich foods plant foods that also contain oxalic acid. Ordinarily, a healthcare practitioner would not discourage a person focused on ensuring that they are meeting their calcium requirements from eating these nutrient-rich foods because of their oxalate content.
Preparation and serving tips
To wash strawberries, dip them in cold water in a large bowl for few seconds and swish gently few times. This helps remove any sand and insecticide/fungicide residues. Then, gently pat them dry using a paper towel or cloth. This method also helps berries bring back to normal room temperature, enriches their flavor and taste. Then remove the stems and caps by simply sniping off with your fingers or using a paring knife.
Here are some serving tips:
- Sliced fresh strawberries can be a great addition to fruit or green salad.
- They can be a great snack between meals. Dried strawberry slices can be added in muffins, pie, cakes and are used in cereal flakes as a breakfast meal.
- The berries are a popular addition to dairy products; as in strawberry flavored ice cream, milkshakes, smoothies and yogurts.
Strawberry smoothie. This health-promoting smoothie recipe provides a wonderful combination of flavors and nutrition to your Healthiest Way of Eating. The addition of tahini helps keep you satiated for a longer period than your usual smoothie (Figure 66).
Prep and cook time: 5 minutes.
The nutritional profile for one serving (232.80 grams) is of 174 Calories.
In order to better help you identify recipes that feature a high concentration of nutrients for the calories they contain, we created a Recipe Rating System. This system allows us to highlight the recipes that are especially rich in particular nutrients. The following chart shows the nutrients for which Strawberry Smoothie is either an excellent, very good, or good source (below the chart you will find a table that explains these qualifications). If a nutrient is not listed in the chart, it does not necessarily mean that the recipe doesn't contain it. It simply means that the nutrient is not provided in a sufficient amount or concentration to meet our rating criteria. (To view this recipe's in-depth nutritional profile that includes values for dozens of nutrients - not just the ones rated as excellent, very good, or good - please use the link below the chart.) To read this chart accurately, you'll need to glance back up to see the ingredients used in the recipe and the number of serving sizes provided by the recipe. Our nutrient ratings are based on a single serving. For example, if a recipe makes 4 servings, you would be receiving the nutrient amounts listed in the chart by eating 1/4th of the combined ingredients found in the recipe. Now, returning to the chart itself, you can look next to the nutrient name in order to find the nutrient amount it offers, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this recipe and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S.
- 4 large strawberries
- 1/4 cup low-fat plain yogurt
- 1 cup fresh orange juice
- 1 TBS tahini
- 1 medium size banana
- 1/2 tsp vanilla
- 1 TBS honey
Fresh berry dessert with yogurt and chocolate. This 10-minute dessert combines our favorite flavors in a quick and easy way that is rich tasting, yet healthier than many desserts. The chocolate is a great complement to the berries and yogurt. It is perfect for those moments when you want to enjoy this wonderful combination of flavors (Figure 66).
Prep and cook time: 10 minutes.
- 1 basket fresh strawberries or raspberries
- 230 g low-fat vanilla yogurt
- 60 g net-wt dark chocolate
Serves 2. For a more formal presentation you may want to pour a pool of yogurt on a plate and place berries on top of pool. Drizzle chocolate over berries.
- Fold together yogurt and berries.
- Melt chocolate in a double boiler with heat on medium. Place berries and yogurt in individual bowls and drizzle with melted chocolate.
In order to better help you identify recipes that feature a high concentration of nutrients for the calories they contain, we created a Recipe Rating System. This system allows us to highlight the recipes that are especially rich in particular nutrients. The following chart shows the nutrients for which 10-Minute Fresh Berry Dessert with Yogurt and Chocolate is either an excellent, very good, or good source (below the chart you will find a table that explains these qualifications). If a nutrient is not listed in the chart, it does not necessarily mean that the recipe doesn't contain it. It simply means that the nutrient is not provided in a sufficient amount or concentration to meet our rating criteria. (To view this recipe's in-depth nutritional profile that includes values for dozens of nutrients - not just the ones rated as excellent, very good, or good - please use the link below the chart.) To read this chart accurately, you'll need to glance back up to see the ingredients used in the recipe and the number of serving sizes provided by the recipe. Our nutrient ratings are based on a single serving. For example, if a recipe makes 4 servings, you would be receiving the nutrient amounts listed in the chart by eating 1/4th of the combined ingredients found in the recipe. Now, returning to the chart itself, you can look next to the nutrient name in order to find the nutrient amount it offers, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this recipe and nutrient, and the rating we established in our rating system.
Kiwi Mandala. Add a bit of sweet to your Healthiest Way of Eating with this mosaic of kiwifruit and strawberries. Most people don't realize that a kiwifruit has more vitamin C than an orange.
Prep and cook time: 10 minutes
Optional: 2 TBS chopped walnuts or pecans, orange zest for topping.
- 230 g low-fat vanilla or soy yogurt
- 3 TBS fresh orange juice
- 1 TBS cream honey*
- 1/2 tsp grated orange rind**
- 1/4 tsp grated lemon rind**
- 1 kiwifruit
- 4 strawberries
About the nutritional profile a portion of 242 g has 167 calories.
- In a small bowl, whisk the yogurt, orange juice, honey and grated orange and lemon rind, making sure the honey is completed blended into the yogurt.
- Place in 2 shallow soup dishes.
- Peel the kiwifruit and slice into 0.3 cm rounds.
- Take the stems off of the strawberries and cut them lengthwise into 4 pieces.
- Arrange the fruit in a beautiful pattern on top of the yogurt mixture and sprinkle with some grated orange rind and nuts if desired.
- Refrigerate for 1/2 hour so that the yogurt is well chilled.
In order to better help you identify recipes that feature a high concentration of nutrients for the calories they contain, we created a Recipe Rating System. This system allows us to highlight the recipes that are especially rich in particular nutrients. The following chart shows the nutrients for which 10-Minute Kiwi Mandala is either an excellent, very good, or good source (below the chart you will find a table that explains these qualifications). If a nutrient is not listed in the chart, it does not necessarily mean that the recipe doesn't contain it. It simply means that the nutrient is not provided in a sufficient amount or concentration to meet our rating criteria. (To view this recipe's in-depth nutritional profile that includes values for dozens of nutrients - not just the ones rated as excellent, very good, or good - please use the link below the chart.) To read this chart accurately, you'll need to glance back up to see the ingredients used in the recipe and the number of serving sizes provided by the recipe. Our nutrient ratings are based on a single serving. For example, if a recipe makes 4 servings, you would be receiving the nutrient amounts listed in the chart by eating 1/4th of the combined ingredients found in the recipe. Now, returning to the chart itself, you can look next to the nutrient name in order to find the nutrient amount it offers, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this recipe and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S.
Strawberries with chocolate creme. Preparetion and cooktime: 10 minutes.
- 3 TBS low-fat vanilla or soy yogurt
- 3 TBS organic cocoa
- 3 TBS maple syrup
- 1 pint strawberries
- Whisk yogurt, cocoa, and maple syrup in a small bowl. If your cocoa has lumps, sift it through a strainer before mixing with the other ingredients.
- Place mixture in 2 small sauce cups on a plate and arrange the strawberries around the cups.
- Dip strawberries into the chocolate creme.
In order to better help you identify recipes that feature a high concentration of nutrients for the calories they contain, we created a Recipe Rating System. This system allows us to highlight the recipes that are especially rich in particular nutrients. The following chart shows the nutrients for which 10-Minute Strawberries with Chocolate Creme is either an excellent, very good, or good source (below the chart you will find a table that explains these qualifications). If a nutrient is not listed in the chart, it does not necessarily mean that the recipe doesn't contain it. It simply means that the nutrient is not provided in a sufficient amount or concentration to meet our rating criteria. (To view this recipe's in-depth nutritional profile that includes values for dozens of nutrients - not just the ones rated as excellent, very good, or good - please use the link below the chart.) To read this chart accurately, you'll need to glance back up to see the ingredients used in the recipe and the number of serving sizes provided by the recipe. Our nutrient ratings are based on a single serving. For example, if a recipe makes 4 servings, you would be receiving the nutrient amounts listed in the chart by eating 1/4th of the combined ingredients found in the recipe. Now, returning to the chart itself, you can look next to the nutrient name in order to find the nutrient amount it offers, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this recipe and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S.
Figure 66 - Some preparation and serving tips: strawberry smoothie; fresh berry dessert with yogurt and chocolate; kiwi mandala; strawberries with chocolate creme.
Strawberries may cause serious allergic reactions in some sensitized individuals. Some of the most common symptoms of strawberry allergy include swelling and redness of mouth, lips and tongue, eczema, hives, skin rash, headache, runny nose, itchy eyes, wheezing, gastrointestinal disturbances, depression, hyperactivity and insomnia. Individuals who suspect allergy to these fruits may want to avoid them.
Producers, farms, import and export of strawberries
Nowadays, there are many farms and agricultural entrepreneurs who work in the sector of fresh and seasonal fruit. In particular, as mentioned before, the processing of strawberries, the trade of strawberries, the production of strawberries and the sale of strawberries are more and more profitable activities for the fruit and vegetable sector: these are certified companies for the production of strawberries and of other fruit and vegetable products, that have a EU certification. Thanks to our yearbooks FruitNEWSLETTER and MEC Ortofrutticolo (and their digital versions) you can easily contact fruit and vegetable companies to obtain information about them all over the world. In particular you can find a list of companies that:
Furthermore, as to this specific cultivation, very important in the fruit and vegetable sector, we give you the opportunity to access to zipmec.eu, the biggest search engine for fruit and vegetable companies all over the world, where you can obtain information on:
- produce strawberries (certified companies for strawberries;
- companies that produce specific varieties of strawberries,
- farms that produce organic strawberries that deal with the trade of strawberries,
- retailers of strawberries,
- wholesalers of strawberries,
- import and export of strawberries (importers of strawberries and exporters of strawberries) and
- operators in the wholesaling of strawberries.
Easily accessible and always up-to date. It is a list of companies for the production of strawberries , the retailing of strawberries, the sale of strawberries, the import/export of strawberries, the wholesale of strawberries, and in general of any company present on the fruit and vegetable market that deals with the production and the trade of strawberries. Apart from companies involved in the European fruit and vegetable sector, of course you can find also lists and information of any company of the world fruit and vegetable market.
- companies that produce strawberries;
- companies with certification for the the production of strawberries;
- producers of strawberries;
- companies that produce organic strawberries;
- companies that deal with the the trade of strawberries;
- retailers of strawberries;
- wholesalers of strawberries;
- importers of strawberries;
- exporters of strawberries;
- operator in the wholesaling of strawberries.
The MEC Ortofrutticolo catalogue describes many varieties of strawberries: it shows for each specific variety of strawberries, agronomic and morfological characteristics, with a picture of the product. For each variety the MEC Ortofrutticolo shows the list of companies tha deal with that specific variety of strawberries, such as producers of strawberries, retailers of strawberries, wholesalers of strawberries, importers and exporters of strawberries, specifying for each fruit and vegetable company its address and any website, in order to contact directly the retailer of strawberries and of organic strawberries.
MEC Ortofrutticolo describes many varieties of strawberries: for each indicates the morphological and agronomic characteristic, with a picture of the products.
In the catalogue you can find the product's characteristics, such as shape, colour of the skin and of the flesh.
For each variety of strawberries, MEC Ortofrutticolo shows a list of companies for strawberries such as producers of strawberries, retailers of strawberries, wholesalers of strawberries, importers of strawberries and exporters of strawberries, specifying for each fruit and vegetable company its address and the website, so that you can contact the producer and the retailer of strawberries directly.
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Fiume Francesco 2005