Strawberry Agronomy Guide


Description

Strawberries are a self-pollinating crop that can be grown as an annual or a perennial. Each plant has a crown and runners. The crown serves as the main growing point. From the crown, leaves, runners, flowers and fruit grow. Plus, branch crowns may emerge from division of the original crown. The branch crowns do not grow their own roots, but they do produce their own leaves and flowers. Runners grow during the summer and produce daughter plants.

Strawberry varieties are classified as June-bearing and day-neutral or everbearing. Each type flowers at a different time. June-bearing varieties produce fruit in the early summer, and everbearing or day-neutral varieties produce fruit throughout the growing season. Everbearing cultivars begin to flower once days provide more than 12 hours of light. On the other hand, day-neutral varieties are insensitive to day length, and they flower continuously. Generally, day-neutral berries perform best in cooler regions, and June-bearing strawberries are the most commonly grown varieties.

Site Selection 

Strawberry planting sites should have soils that are free of plant residues, stones and sticks and have a pH level between 6.0 and 7.0. Additionally, sandy loam, clay loam or silt loam soils are best.

To control insects and diseases and promote good yields, rotate strawberries every few years. If possible, then don’t plant strawberries to follow soybeans, field corn, tobacco or other plants that had herbicides or plant growth regulators applied. Those applications can leave residues that could harm strawberries and potentially reduce yields. Additionally, strawberry plants should not be rotated with crops susceptible to Verticillium wilt; examples include strawberries, raspberries, potatoes, peppers, eggplants and tomatoes. When choosing a site, also avoid areas with perennial weeds and those that have recently grown sod. Sod can harbor white grubs, which damage strawberry roots.

Selecting a site with proper air and water drainage is vital to growing strawberries. Because strawberries cannot tolerate standing water, avoid low, wet and poorly drained areas. To reduce the risk of standing water, consider tiling, planting on ridges or using raised beds. Adding organic matter to the soil can encourage good water drainage, and choosing a sloping site that is more elevated than the surrounding land can promote proper air drainage. Exposure to direct sunlight assists in drying fruit and foliage after irrigation.

If growing strawberry plants as an annual crop in a plasticulture system, then using raised beds is key because water can more readily run off. Plasticulture systems enable growers to produce berries earlier in the season. Strawberries can also be grown in high-tunnel systems. The semi-permanent structures covered with plastic allow producers to extend the harvest season and better control the growing environment.

Fertility
Generally, a soil’s nutrient levels are adequate for growing strawberries, but in order to fully gauge fertilizer needs, a soil test should be conducted. Many strawberry operations apply 30 pounds to 80 pounds of nitrogen per acre. In the bed center, nitrogen should be banded 4 inches deep in split applications — once prior to planting and once during running. Both too little and too much nitrogen can affect strawberry plants. Applications of nitrogen are required annually at renovation.

Depending on soil test results, 40 pounds to 70 pounds of phosphorous per acre can be worked into the soil as a preplant fertilizer with a perennial matted row system. Between 45 pounds and 80 pounds of potassium are also typically incorporated into the soil prior to planting. Annual soil tests should be conducted to ensure soil nutrient levels are optimal.

Farmers growing strawberries in the annual plasticulture system commonly apply pre-plant 60 pounds nitrogen (N) per acre, 60 pounds phosphate (P2O5) per acre and 120 pounds potassium (K2O) per acre, which is mixed into the bed.  Apply phosphate or potassium as indicated by a soil test. Additional nutrients are injected through the trickle irrigation system in the fall and spring as indicated by foliar tests.

Variety Selection 

Suitable strawberry varieties for growing in Missouri include Annapolis, Earliglow. Redchief, Delmarvel, Honeoye, Surecrop, Mesabi, Jewel, Allstar and Lateglow. These varieties have varying tolerances to anthracnose, reach maturity at different times — see table below — and have varying cold resistance levels. To extend the harvest season, many strawberry growers select several cultivars of varying maturities.

Strawberry Cultivars for Missouri

Variety Season
Annapolis

Earliglow (Earlyglow)

Redchief

Delmarvel

Honeoye

Surecrop

Mesabi

Jewel

Allstar

Lateglow

Early maturing

Early maturing

Mid-season

Mid-season

Mid-season

Mid-season

Mid-season

Mid-season

Late maturing

Late maturing

 

Planting

A matted row system is commonly used to raise June-bearing strawberries. In this system, mother plants produce runners, which develop into daughter plants. These daughter plants ultimately form a matted row of plants. For matted row production, plant strawberries in early spring in rows spaced 3 feet to 4 feet apart. Within a row, allow 1.5 feet to 2 feet of space between individual plants. Soaking plugs in water for a few hours prior to planting can be beneficial. In a matted row system, flower clusters should be removed during the first year in order to encourage the young plants to form runners and grow.

In a plasticulture system, strawberry plugs are transplanted into raised beds that are 8 inches to 10 inches tall and 29 inches to 30 inches wide. As a general guide, transplanting should occur during late August. If using high tunnels, then transplanting can occur later in mid-September. Beds should also be debris-free. In these beds, space strawberries at 12 inches to 15 inches apart. Beds should be fitted tightly with black plastic mulch. When planting transplants, make sure not to plant too deep or too shallow. In either case, plants could die. The midpoint of the crown should be level with the soil surface. If planting strawberries in a high tunnel, plant on raised beds in double rows to maximize the use of space.

Cultural Management 

Strawberries are self-pollinating plants, but if wild bees are not plentiful, then adding one strong bee colony per acre of strawberries is recommended and may enhance fruit size and weight. Honeybees are the most effective pollinators for strawberries, but bumblebees can be used as an alternative.

In a high-tunnel system, bees are necessary. One strong hive is needed for each tunnel, but substantial bee losses may prompt hives to be replaced. If honeybee hives are implemented in high tunnels, avoid UV glaze protectants on tunnels. For both honeybees and bumblebees, make sure to move hives prior to applying pesticides. After temperatures exceed 50°F, opening the tunnels can facilitate wind and native bee pollination. Black plastic mulch should also be used when growing strawberries in high tunnels.

In a matted row system that grows strawberries as a perennial crop, strawberry plants should be mulched in the fall to ensure winter survival. Fields should be covered in a straw or corn stalk mulch that is 2 inches to 3 inches deep. In the spring as the strawberry plants begin to grow from crowns, remove mulch. Workers can rake the mulch into the alleys between strawberry rows. To protect plants from cold weather, growers may also cover strawberries in a matted row system with row covers.

Strawberries grown in a plasticulture system also benefit from heavy weight spunbonded row covers as they may offer the strawberry plants protection during the winter months. Black plastic mulch on the soil bed itself also helps to capture heat and warm the soil.

Water Management 

Adequate irrigation is a necessity for strawberry production. Overhead sprinkler irrigation is popular when growing strawberries in the Midwest, and strawberries typically require 1 inch to 2 inches of water per week. On days with low humidity and high temperatures, 25 percent to 30 percent more water than is typical should be applied to compensate for moisture losses.

Sprinkler or overhead irrigation is also an effective means of frost protection. Applying 0.1 inch of water per hour when temperatures drop to 34 degrees or colder can provide frost protection as the freezing moisture creates heat as a byproduct, and that heat provides warmth to the plants. Note, in windy conditions, operators may need to apply more water to provide adequate frost protection, and when winds exceed 20 mph, protecting the plants from frost is harder to achieve.

As an alternative to sprinkler irrigation, drip irrigation can help with preventing disease incidence in strawberries because the drip tape doesn’t expose plants to water. Drip irrigation also efficiently uses water and can evenly apply low-pressure water. Additionally, fertilizer can be applied through the drip irrigation system. Drip lines should have 4- to 6-inch dripper spacing. Bury lines 1 inch to 2 inches into the soil. Strawberries grown in a plasticulture system require drip irrigation.

Weed Control 

To minimize weed pressure, select a growing site that lacks perennial or persistent weeds. Applying herbicides is a good strategy to eliminate weeds in the year before planting. Following planting, emerging weed seedlings should be removed. Weeding by hand and using a hoe are two options. Others include applying herbicides and cultivating. Cultivation at weed emergence can effectively remove small weeds, but it must be shallow to prevent damage to roots and above-ground strawberry plant vegetation. By cultivating at a shallow depth, you also prevent diluting pre-emergence herbicides.

Insects and Diseases

Several types of insects pose a challenge to strawberry production as they can damage fruit or foliage. They include slugs, strawberry clippers, sap beetles, spittlebugs, strawberry rootworm, strawberry root weevil, eastern flower thrips, spotted wing drosophila and tarnished plant bug. To minimize insect pressure, choose an appropriate growing site, and rotate crops. If faced with an insect outbreak, then chemical controls may not be fully effective because insects can recolonize strawberry fields quickly. If using insecticides, then time the application to prevent bee kills.

Other pests known to target strawberry plantings include birds, turkeys and deer. Birds and turkeys can feed on strawberries. Netting, sound devices or visual devices — examples include artificial predators and humming lines — are tools to deter birds and turkeys. Deer, which forage on strawberry foliage, can be deterred by adding odorous materials such as human hair or soap to a strawberry field. Additionally, to repel deer, growers can startle them with unfamiliar sounds and set up physical barriers such as fences.

Diseases that can affect strawberry crops include botrytis blossom blight, botrytis fruit rot, various fungal leaf spots, anthracnose, leather rot, Verticillium wilt and red stele. Rotating strawberries is critical to preventing diseases. Avoid choosing a growing site that has grown crops susceptible to Verticillium wilt in recent years. Crops that are susceptible to Verticillium wilt include potatoes, peppers, eggplants, melons, okra, brambles and tomatoes. Additionally, choose cultivars that tend to resist troublesome diseases. Strawberries grown in a high tunnel are especially susceptible to gray mold. Avoid high humidity and excessive nitrogen fertilization within the high tunnel to prevent gray mold. Labeled fungicides are commonly used to manage strawberry diseases.

Harvest, Storage and Post-Harvest 

Strawberries require hand-picking at least three times a week during the harvest season. For optimal flavor, harvest when a berry’s shoulders and tip no longer show any green or white. If hiring labor, then assume that one acre requires six to nine people for harvest. Operating a pick-your-own strawberry patch can serve as an alternative to hiring pickers.

After picking, store berries at 32°F to 35°F. Strawberries generally maintain good quality for up to seven days if stored at the proper temperature. To maintain their quality, strawberries require a storage environment with 90 percent to 95 percent relative humidity. Adding carbon dioxide to the storage environment at levels between 10 percent and 15 percent can extend shelf life; dry ice can produce the necessary carbon dioxide.

In an annual production system, destroy strawberry plants immediately following harvest in order to prevent disease and mite infestations. Both may threaten future crops. In a matted row system, fields should be renovated within seven days to 14 days after the end of harvest. Renovating fields involves mowing off strawberry foliage at 1 inch to 2 inches above the crown; at this height, the mower will be less likely to damage crowns. In order to prevent plant overcrowding, which reduces quality and yield, strawberry rows should be hand-hoed or narrowed to a width of 12 inches to 14 inches using a tiller. Narrow rows help to improve sunlight penetration, control disease and enhance fruit quality. During the renovation, also apply fertilizer and herbicides as needed.

Sources

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