Frigo plants are one-year-old young strawberry plants kept in a cold store, used to set up fruiting plantations. These young plants are dug out in November or December and when runners and leaves have been removed, are stored at a low temperature (minimum - 2° C). They can be kept in such conditions until July of the following year. Depending on the situation, they can be used at any time and planted both in the open field or under cover. They give their first yield 8-10 weeks after planting and in the following seasons they bear fruit at the characteristic time for each particular variety.
They allow controlled strawberry production.
They guarantee very good acclimatization often without watering.
Their use eliminates the risk of freezing during winter.
They ensure a uniform and vigorous growth, which facilitates a safe and timely use of plant protection formulations.
They restrict the spread of leaf diseases such as Common leaf spot caused by Mycosphaerella fragariae or Powdery mildew caused by Sphaerotheca macularis.
Controlled strawberry production lies in the possibility of crop harvesting at the time thought to be optimal by the producer when considering economic and agricultural factors. Speeding up or delaying fruiting can be obtained by means of production under covers or by using frigo plants. Alternatively, both methods can be combined. The period of time from planting to fruiting varies from 8 -10 weeks. The best cultivars for controlled production are: Vibrant, Elegance, Elsanta, Kent, Honeoye, Matis and Florence.
The yield should amount to 3-4 tons per hectare for standard plants with a crown diameter of 8-15cm and 6-8 tons for A+ plants with a crown diameter of more than 15cm.These yield estimates are relative to the standard density of 40 thousand plants per hectare, provided that both appropriate protection and good production practices are applied.
Strawberry plants like light and aerated soil. The most important requirement is to ensure regular irrigation. Heavy, non-aerated, damp soils are not a good environment for strawberry plantations. It is not advisable to set up a strawberry plantation immediately after another plantation of strawberry, vegetable, horticultural or potato plantation, because of dangerous diseases and soil pathogens. The best preceding crops are plantations of cereals, Cruciferae (rape-seed, white mustard) or papilionaceous plants (Fabaceae).
When complex mineral fertilization is applied, the use of organic manure is unnecessary. Complete fertilizers are most effective when applied a few months before plantation setting. If pressed for time, the best way is to apply chloride -free fertilizers. This plantation setting should always be preceded by a thorough chemical soil analysis (acidity, content of P, K, Mg), which should be carried out at specialized centers.
In the case of increased acidity (ph <5.0) the best, fastest and safest way is the application of chalk calcium. The efficient eradication of permanent weeds is essential for the preparation of the strawberry production field and the best way to do this is by using gliphosphate. If the field is heavily infested with weeds, it is recommended to perform the chemical treatment twice, allocating the whole season for this purpose. In the case of the most resistant weeds, such as horsetail (Equisetum) or weeds of the Rorippa sylvestris, it is advisable to add Starane and Chwastox Extra to gliphosphate. The soil should rest for 2-3 weeks after the mechanical cultivation. Just before planting, which is especially important in spring, the germinating weeds should be destroyed chemically (Reglone or Basta) or by superficial mechanical means.
Industrial cultivars: Senga Sengana, Dukat, Polka
Fresh fruit cultivars: Kent, Honeoye, Elsanta, Marmolada, Pegasus, Florence, Albion, Elegance, Vibrant, Matis
A detailed description of the most valuable cultivars can be found in the link: Variety descriptions.
The plants should be planted at the right depth: not too shallow, not too deep and the roots must not be folded in any way. One of the common mistakes made while planting strawberry plants is to let them dry, especially their roots. It is then essential to sprinkle the green plants abundantly with water, or in the case of frigo plants, to protect the boxes from the sun. While planting these plants into freshly prepared soil, it is necessary not to plant them too shallowly. If the roots are very long, it is better to shorten them rather than accidentally fold them up. It is a big mistake to place the plants too deeply, because it stops them from growing in the first phase after planting. When the stock is planted, especially the green plants, the whole plantation should be irrigated. It is of a great importance to keep the proper spacing while planting. Precise spacing pays off later during agricultural and chemical treatments.
It is necessary to provide the newly planted stock with sufficient amounts of water during the first weeks after planting. Fertilization should be started when the plants start to show signs of regular growth - when 2-3 new leaves appear (after 3-4 weeks ). The first fertilization should not exceed the dose of 0.6 kg of fertilizer per 100 meters of the row. The safest fertilizers in this phase are the slow-release fertilizers, e.g. Agroblen or Agromaster. Special attention should be paid to the doses of NO3 – form fertilizers. The general rule is to use all fertilizers (especially nitrogen) often but in low doses.
This should be started with an efficient eradication of perennial weeds using herbicides prior to plantation setting. The best efficacy can be obtained by combined treatments with gliphosphate and Chwastox Extra. Annual weeds can be destroyed mechanically by harrowing, or chemically using Reglone directly before planting. Two weeks after planting, we start to destroy annual weeds with Betanal. This formulation treatment should be applied as split sprays at 10-14 day intervals. The use of soil-applied herbicides such as Venzar should be postponed as far as possible. One month after planting seems to be the best time for this kind of treatment. An exception is Devrinol, which should be applied in the dose of 2-2.5 kg/ha straight after planting. It is not adviceable to do any mechanical cultivation during treatments with herbicides because it induces the growth of new weeds. Any weeds which have not been destroyed chemically, can be pulled out by hand or eradicated by shallow hoeing. Grass weeds on fruiting plantations can be eliminated at the time of their intense growth using Targa or Fusilade. All chemicals must be applied according to the instructions in the label, paying particular attention to their withholding period. It is worth remembering that chemical treatments can be harmful. Particular attention must be paid to the use of soil-applied herbicides on light soils, and also to the susceptibility of some cultivars to herbicides and other chemicals. The doses of soil-applied herbicides on plantations older than one year can be increased by 50%.
The main reasons for failure in strawberry production are:
the wrong choice of cultivar
poor quality of the planting stock (dried, diseased or infested plants)
badly prepared field or wrong crop rotation
high doses of fertilizer soon after planting
insufficient or unskillful weed control
inefficient protection against pests and diseases
no mulching with straw, which decreases the quality of fruit especially for fresh use
no fruit cooling after harvest
inappropriate packing of harvested fruit
Prevention plays the most important role in the fight against diseases caused by Verticillium and Phytophthora. This can be achieved by the following:
healthy nursery stock
appropriate crop rotation
the right choice of cultivars resistant to the pathogens
the right choice of light aerated soils
If the risk of root diseases is high, it is recommended to soak the roots in a 0.3% solution of Aliette or 0.2% solution of Topsin prior to planting. The most susceptible cultivars are : Elsanta, Honeoye and Kent.
Nursery stock from certified nurseries should be free from cyclamen mites. However, it may happen that this pest exists below the treatment thresholds, which deceives the stock growers and plantation owners. High propagation capabilities and the quick spread of this pest (cultivation equipment, protective clothes, wind) could, in favourable conditions, lead to a situation which becomes uncontrollable in a short time. The proximity of old infested plantations also increases the risk of mite occurrence in the new ones. It is necessary to carry out prophylactic treatments on plantations which cannot conduct proper monitoring of this pest, especially after setting new plantations. Only then can it provide an effective protection, ensuring that the pest will be restricted or even completely eradicated. The best time to protect the new plantations is spring (April or May), when the temperatures exceed 12-15°C. At this time the newly set plantations are in the phase of 3-4 leaves, which facilitates their thorough spraying. The most effective formulations during this period are those containing abamectin: Vertigo 018EC, Promektyna 018EC and Acaramic 018EC. This thorough plant spraying requires a large amount of water - at least 1000 l/ha with the addition of a surfactant. A more economical method is to only spray the plant rows and not the whole field area. Abamectin manifests stomach and contact action on the pest and only eliminates mobile forms of it. In order to get rid of the new generation of pests from eggs, the treatment should be repeated after 7 days. In the 2013 season there will be a new formulation registered in Poland - Movento 100 SC, with its active compound spirotetramat, which can be used to fight strawberry mites. Unlike other compounds, it has a systemic mode of action, which ensures better efficacy with a smaller amount of water (500-700 L/ha). The recommended dose of this new formulation is 1-1.5L/ha. The systemic property of spirotetramat gives the possibility to perform this application at later times than with abamectin. The application should be repeated after 7-10 days.
European tarnished plant bug (Lygus rugulipennis) is a mirid 5.0-6.0mm long, feeding on flower buds, flowers and small fruits. The nymphs can be mistaken for aphids, but unlike them they, move quickly. This pest sucks the fruits causing fruit malformation. It is worth remembering that similar deformation can be caused by insufficient pollination during cool weather. This bug is particularly dangerous for late season varieties and everbearers, because its life cycle falls in summer and autumn. This pest feeds on many plant species and also weeds, so the essential method of control is eliminating weeds on the plantations and in the surrounding areas. Strawberry flowers are most endangered from the time when they start to separate into clusters until about 10 days after the petals fall off. It is very important to monitor the presence of nymphs in this particular period of time. The best way to do that is to shake off the pests from the flowers onto a white piece of paper. The treatment threshold is 2 pests per 200 flower clusters. The first generation of this bug is eliminated alongside with strawberry blossom weevil , therefore it is mildly dangerous in well-protected plantations. However, in June and July the second generation appears, which poses the highest danger. The second generation of bugs fly from the infested weeds onto the flowering strawberries. It is a big mistake to mow the weeds or surrounding plantations in blossom because it enhances the migration. As far as everbearing cultivars are concerned e.g. Albion, the most important action is to use chemical treatments implemented about 3 weeks prior to ripening if the first flowers were nipped. Two treatments with Mospilan 20SP in the doses of 0.15-0.20 kg/ha are recommended with about 750 L of water per hectare, using a sprayer with additional air flow. This treatment should be repeated after 10-12 days, paying particular attention to the 14-day withholding period. It is also recommended to apply pyrethroids with a short withholding period - Decis Mega 50 EW (3-day withholding period) or Karate Zeon 050 CS (7-day withholding period). Alternately, both formulations in the dose of 0.15-0.20 L/ha can be applied at the ripening time. They must be applied at temperatures below 20°C, best in the evening.
The most important factors determining success in plantations of everbearers are:
the right choice of the cultivar
certified nursery stock from a certified grower
starting production on relatively small fields and gradually increasing the production area
early planting with the option of a one-year cultivation
elimination of early flowers and in this way obtaining more time for protection against pests and diseases
effective fertilization - relatively frequently and at small doses (in total 70-90 kg N/ha)
appropriate protection against frost is recommended although everbearers affected by frost regenerate quite well The most important factors influencing health status (not only applicable to everbearers) : - plant vigour - which depends on the chill accumulated in the stock and skillful fertilization
protection against stress - too high a temperature, insufficient irrigation and harmful pesticides
the right humidity of soil - planting on elevated beds
the right choice of soil - avoiding heavy, damp soils with poor drainage
avoiding intense fertilization, especially with nitrogen, which induces most fungal diseases.
a wise use of fertilization, which should only be used when necessary
isolation of new plantations from the old ones already infected by pests and diseases
weed control - they are an indirect source of pests and pathogens
cultivar resistance to pests and diseases
appropriate irrigation, recommended drop irrigation
mulching with straw, which restricts water flow in the furrows and consequently the spread of fungi.
At present the best everbearing variety for Polish conditions is Albion and derived cultivars such as San Andreas, Monterey and Portola. The main marketable features of these varieties are the excellent taste, high durability and attractive looks, which makes producing them profitable and their share in the total production is growing systematically. Many cultural factors influence the results of everbearing plantations. However, the final success comes from the interaction of these factors in the whole production cycle. American growers emphasize that the most important challenge for the producer is to keep the right balance between the vegetative growth (leaves and roots) and generative growth (flowers and fruit) during all production stages. Only such an approach can bring good, high quality yields.
Planting material from certified nurseries gives growers the guarantee of variety purity and a good health status. Using planting material from old fruiting plantations or from an uncertain source, is risky and unprofitable. Old plantations should be regarded as a hotbed of dangerous diseases and pests.