Horticultural Crops
Small Fruit

Small Fruit

When growing small fruits, growers must provide an environment that reduces the risk of pests and disease while keeping plants healthy. The result will be a good yield of high-quality fruit. Consumers are increasingly concerned about environmental issues such as pesticide use. Fortunately, by using best management practices, the need for pesticides may be reduced.

The goal in small fruit production is high yield of quality fruit while preserving the environment for future production.

Soil Management

When planting small fruits such as strawberries, raspberries and blueberries, it is important to start planning and making changes at least a year before establishment takes place. Follow these steps:

Soil test - this will provide a reading of soil nutrients, organic levels and pH. Interpret results carefully. Even minor imbalances may cause problems to crops. Adjust soil pH to the following levels: 6.5 for strawberries and raspberries and 4.5 to 5.2 for blueberries.

Prepare site - the year before planting, consider soil fertility, organic matter levels, perennial weeds, drainage, pest levels and soil pH and improve where possible. Examine previous soil test results, earlier crop histories and drainage.

Determine nematode populations - if the site was planted in other small fruits or in orchards, take a soil sample to determine nematode populations. Nematodes damage roots and allow diseases to attack. If counts of root lesion nematodes exceed 500 per kilogram of soil, plants may be stunted and unhealthy. For raspberries, counts of 100 dagger nematodes per kilogram heighten risk of Tomato Mosaic Virus (Crumbly Berry Disease).

Alternatives to chemical fumigation include:

• Allowing soil to lay fallow for at least one full growing season in a weed-free condition. While this reduces pest risk, it may cause erosion and breakdown of soil structure.
• Planting cover crops for one year prior to the fruit crop. Use alfalfa, brome hay or another crop that suppresses nematodes.

Organic Matter

Increasing organic matter levels in the soil will improve its ability to hold water and nutrients. If a soil test shows organic matter levels are low, consider using cover crops, or adding manure, straw or hay.

Tillage, including cultivation between rows, breaks down organic matter. To reduce loss, reduce the depth and amount of tillage.

In established raspberry and blueberry fields, permanent sod between rows will reduce soil compaction and erosion, improve soil organic matter levels, make harvesting easier and moderate soil temperatures. The recommended grass for sod cover is Creeping Red Fescue and mixes containing it. This species is relatively resistant to equipment traffic, moderately vigorous and becomes dormant in hot summer months when the crop needs available moisture.

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Mulches

The use of wheat straw mulches controls winter injury to strawberries. Mulches are also useful during the growing season to control fruit rots, especially Leather Rot. Mulch keeps berries off soil which reduces the spread of fungi to fruit. When the mulch is worked into soil, it adds to the organic matter levels. Timing of mulch application is important. If it is applied too early, plants don’t harden; if applied too late, winter injury is possible.

With blueberries, a layer of permanent mulch at the base of bushes is essential. Since blueberry roots are shallow, the mulch will preserve soil moisture, decrease soil temperature during the summer, protect roots from winter injury, increase organic matter and provide weed control. Mulches may be sawdust, wood chips, chipped brush or acidic peat moss. If finding mulch is difficult, produce your own by chipping brush and composting it for a year. Some hardwoods, such as walnut, and softwoods, such as cedar, may cause crop growth problems.

Mulching can be used in raspberry production to control soil temperature and to conserve moisture.

Straw mulches in strawberries control winter injury, but also keep berries off the soil reducing the spread of fruit rots.

Soil Compaction

Soil compaction is evident in areas that are highly-travelled such as alley ways between strawberry rows and grass strips between raspberries and blueberries. In strawberries, subsoil the alley way when necessary depending on soil type and the amount of traffic. In sod fields, the use of mechanical aerators will have the same effect. Dry soil conditions are necessary for the most effective use of these techniques.

Water Management

Drainage is important for productive small fruit crops. Standing water and water-saturated soils increase the development and spread of disease and increases the chance of winter injury damage. Prior to planting, establish tile drainage and good surface drainage.

Irrigation of small fruits is important. Small fruits have shallow roots; proper moisture levels must be maintained. Irrigation cools the soil around the roots which encourages root growth. Water is also important when fruit is growing and in the late summer during bud initiation. Trickle irrigation is best suited for raspberries and blueberries. Overhead irrigation does require large volumes of water. However, it can also be used for frost protection in strawberries and low bush blueberries.

Two Best Management Practices for blueberries include using a combination of a sod ground cover and trickle irrigation.

Begin irrigation when at least 50% of the moisture in the soil has been used. Trickle irrigation should begin early in the season since small amounts of water are applied at a time. Continue irrigation until after harvest to ensure proper plant growth and bud initiation for the next season.

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Nutrient Management

Test soils annually to see what nutrients are needed. Also, test leaves to determine nutrient levels. Your fertilizer program can then be fine-tuned for each field. The amount of fertilizer will depend on yield goals, planting density, soil type and the crop. For example, blueberries may need sulphur-based fertilizers to keep soil pH levels low.

Foliar micronutrients are helpful in adjusting nutrient deficiencies. They allow rapid responses. Visual inspection and leaf analysis will indicate need.

A strawberry plant's water requirement through a typical growing season. Peaks on the graph indicate periods when water is particularly important for the plant part listed on the left.

Text Equivalent

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Pest Management

The use of pesticides in small fruit production controls weeds, insects and diseases. Before deciding on control, monitor fields closely to understand pest problems. Keep a record of each field’s crop history and previous problems. Any field with a history of Verticillium wilt, Red steele and Black root rot should be avoided. Don’t plant into a field that has recently grown tomatoes, peppers, eggplant, melons, raspberries or strawberries. Allow at least two years between small fruit crops. Also, consider herbicide residues or carryover. An Integrated Pest Management system, including monitoring, timing of sprays and cultural practices, will help to reduce the amount of pesticide used on a crop.

Cultural Control

Crop rotation reduces weed problems and may reduce disease and nematodes.

Select varieties to minimize disease.

Pruning and trellising decreases insect and disease pressure by allowing better movement of air and better penetration of pesticides.

Weed control along the perimeters of the field will eliminate hosts for insects.

Cane density pruning to 10 to 15 canes per metre and maintaining narrow raspberry row width (30 cm) increases light penetration and improves yields.

Monitor small fruits and keep good records to better time sprays and cultural practices.

Biological Control

• Parasites and predators occur naturally in the environment and feed on insect pests. Avoid pesticides that will harm these.

Chemical Control

Understand the pest’s life cycle and apply chemicals at the stage when the pest is most vulnerable. Rainfall and temperature play an important part in pest development. Monitor your fields regularly and carefully. Some growers hire a scout for weekly or bi-weekly monitoring.

To control disease, apply fungicides before damage occurs. In strawberries, for example, apply fungicide during the bloom period to avoid Botrytis grey mold. One or two well-timed sprays are more effective than five sprays between bloom and harvest.

To control insects, monitor fields closely and spray according to action thresholds established for each insect. In strawberries, for example, 2.25 Tarnished Plant Bug nymphs per 15 flowers is an action threshold indicating that it is time to spray.

Pruning and trellising decreases insects and disease pressure by
allowing better movement of air and better penetration of pesticides.

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Alternative Pest Control

Insecticidal soaps - a two per cent solution, that will control 45% of some insects.

Bug vacs - to suck up insects.

Summary

The production of small fruits is intensive and costly. Good management must be practised to ensure profitability. By looking at all growing inputs and realizing how they interact, growers can make best management decisions. The goal is to keep yields high but preserve the environment for future production.  

Fruits: Page 4

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