Homeowner - Strawberry Insect and Disease Control

Diseases and insects can limit the production of strawberries in home plantings. Effective disease and insect control depends on a combination of cultural, sanitation, and pesticide application practices. If you follow the proper cultural practices and plant the varieties recommended for your area of the state, you should obtain strong plant growth, and your plants will be less likely to be attacked by insects and diseases. You should have your soil tested and fertilized according to the soil test report. Plant in well-drained soils to reduce the possibility of several root diseases. Thin plant stands after the harvest season to improve air circulation. You should also rotate strawberries with other crops, such as corn or grasses, to help reduce disease and insect problems. Remove weeds and dead or poorly growing strawberry plants from the planting area because they can harbor diseases and insects.

Purchase plants from reputable sources that sell certified disease-free plants. If you grow your own plants, do not use any that you suspect are diseased.

Virus diseases can greatly reduce the yield as well as the quality of strawberries. Virus diseases are often present but not recognized because the symptoms are hard to see. The best way to control virus diseases is to plant only certified virus-free plants. You should not set new plants near old plantings or wild berries. Aphids or mites, most common in the spring or fall, can transmit viruses from plant to plant.

The most common fungal leaf-spot diseases are scorch, powdery mildew, leaf blight, and leaf blotch. Gray mold is the major fruit-rot disease of strawberries. In rainy weather, it can cause 50 percent or more reduction in yield. Defective plant parts are often covered with a fuzzy, gray mass of spores of the fungus.

Leaf spots and fruit rot are controlled through good cultural and sanitation practices and through the use of fungicides. Applying a fumigant, as discussed under Nematode Control, will help control these diseases when strawberries are planted in the same location regularly because some fungi can overwinter in soil and plant debris from one year to the next. Captan, thiram, and benomyl are the commonly used fungicides for control of leaf spots and fruit rots. Apply 3 tablespoons of captan 50% WP, or 2 tablespoons of thiram 65% WP, or 1 tablespoon of benomyl 50% WP per gallon of water. Apply at 7- to 10-day intervals for new growth until harvest. Make more frequent applications during long wet periods. Captan and benomyl can be used during harvest. Thiram should not be used within 3 days of harvest. Follow rates and directions for use as stated on all fungicide and insecticide labels.

The anthracnose fungus causes dark brown, oval sunken areas or spots on stems. It also causes the crown to rot, which may cause young leaves to wilt. The fungus can be carried on apparently healthy plants. Therefore, you should be sure to use healthy certified plants for transplanting. If you avoid excess moisture during the summer, you will help decrease the severity of this disease. Most strawberries grown in Mississippi are susceptible to anthracnose although Apollo seems to be somewhat more tolerant. Anthracnose cannot be adequately controlled through the use of fungicides.

Several nematodes damage strawberries in Mississippi. In affected plants, growth is stunted, older leaves die, and few runners are produced. Symptoms often appear during the summer and can occur in spots within a field. The lesion nematode causes brown spots, or lesions, on the roots. Eventually, the entire root system may turn black. Nematode problems usually occur in soil where strawberries have been planted before. You should have a nematode analysis conducted on soil samples from your garden before planting to determine whether your soil is infested with nematodes. You can get nematode assay bags at your county Extension office. Take at least a pint of soil from several locations in the planting site at a depth of 6 to 8 inches. Although you can take samples at any time, autumn is best. Return the samples to the county Extension office or mail them directly to the Extension Plant Pathology Laboratory, Box 9655, Mississippi State, MS 39762.

MSU-ES Publication 483 suggests the following nonchemical ways to reduce nematodes: sanitation, solarization, fallowing, moving the planting site, and planting masses of certain marigolds. The best way to control nematodes in most situations, however, is to use a multipurpose soil fumigant before planting. In addition to controlling nematodes, the fumigant will also kill many harmful fungi, bacteria, and weed seeds that might be in the soil. SMDC, sold as Vapam, and methyl bromide are available to the home gardener in small containers. Use these chemicals only when you have a nematode problem or when you have had severe disease problems in previous strawberry plantings. These chemicals are expensive and can be dangerous if not handled carefully.

For best results, apply SMDC or methyl bromide to the entire soil surface. When you apply either material, be sure the soil temperature is above 55 °F at a 3-inch depth. Cultivate the soil so that it is free of clods. Apply the fumigant at least 2 to 3 weeks before planting.

It is best to apply SMDC to the entire soil surface. The sprinkling can and hose-end sprayer methods are the most popular and practical ways to apply SMDC. When using the sprinkling can, place 1 pint SMDC in the can, fill with water, and sprinkle evenly over 50 square feet of well-prepared soil. When using the hose-end sprayer, fill container with 1 pint SMDC and spray uniformly on 50 square feet of well-prepared soil. Seal the soil immediately after application to prevent gas escape. To seal the soil, sprinkle thoroughly with water, wetting the soil 3 to 5 inches deep, or place a plastic tarp over the soil for 48 hours. See label for additional information on application directions.

Methyl bromide is extremely dangerous and must be applied under a plastic tarp. Use 1 pound of methyl bromide per 100 square feet of soil. Several methods can be used to release methyl bromide from the can. Refer to the label or Plant Disease Dispatch M-705 to determine which method would be best for you. Make a trench 4 to 6 inches deep around the edge of the area to be treated. Cover the soil with an airtight plastic cover and seal the edges by placing soil into the trench over the plastic before releasing the chemical. Keep the plastic over the treated area for 48 to 72 hours after application. Be sure not to puncture the plastic so that the material will not escape.

These instructions for applying SMDC and methyl bromide are only general guidelines. The final authority for rates, methods of application, and restrictions on these and other pesticides is the label of the package or container. You should wear rubber gloves and protective eyeglasses when applying these chemicals. Always use chemicals with care. Avoid skin contact or inhalation and follow all label directions and precautions. Do not allow children to play around treated areas. Fumigants are highly dangerous.

Black Root-Rot Complex

Plants with black root-rot complex do not grow properly and soon die. The root system will be dark and rotten, and there will be a noticeable absence of small feeder roots. Several different fungi and nematodes cause this disease. If you find this problem in a home planting, find a new location. Do not use any plants from an infected field to start your next strawberry planting. If you must replant in infected areas, fumigate the area as described previously before planting.

Aphids are small sucking insects that may cause damage any time. Their feeding causes leaves to curl, and the sticky honey dew that aphids excrete supports sooty mold development. Aphids are capable of spreading virus diseases, and their populations may build up rapidly.

Spider mites also suck sap from the plant and cause loss of plant vigor. Control aphids and mites through thorough coverage. Use 1 1/2 teaspoons of 57% malathion EC per gallon of water or use 2 tablespoons of 25% diazinon EC in 3 gallons of water. A home orchard spray material that contains captan, malathion, and methoxychlor may be used by following the label directions. If malathion does not control the mites, use Kelthane (dicofol).

Ants, white grubs, wireworms, root weevils, crown borers, and mole crickets are soil insects that are best controlled before setting the plants in the bed. These insects feed on the roots and the lower part of the plant. Control by making an application at least 2 weeks before planting. Use 3 1/2 ounces of diazinon 5% granules per 500 square feet of soil area. Apply the insecticide evenly to the soil and disk it in 3 to 5 inches deep.

Plant bugs feed on blooms and young fruit and prevent maturity by causing deformed growth and woody tissue. The adults and nymphs of plant bugs produce the damage by injecting a toxic saliva into the plant when feeding.

Control catfacing insects during fruit production by using a malathion, methoxychlor, and captan mixture or by using a malathion, Sevin, and captan mixture. Mix and apply according to label directions.

These pests feed on fruit on or near the soil. Control snails and slugs with metaldehyde bait. Apply the bait in late afternoon. Do not allow bait to contact fruit. Place it between rows and between plants.

Control of the above-mentioned pests during the fruit production season requires close scouting to determine their presence. It may be necessary to spray on a 7- to 10-day schedule from the time of new growth until 14 days before harvest. However, it may be possible to reduce the number of insecticide applications by scouting. If the insects are not present, only the fungicide spray is needed.

The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended of other products that may also be suitable.

By Dr. James H. Jarratt, Extension Entomologist, and Dr. Frank Killebrew, Extension Plant Pathologist

Mississippi State University does not discriminate on the basis of race, color, religion, national origin, sex, age, disability, or veteran status.

Information Sheet 463
Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published in furtherance of Acts of Congress, May 8 and June 30, 1914. Ronald A. Brown, Director

Copyright by Mississippi State University. All rights reserved.

This document may be copied and distributed for nonprofit educational purposes provided that credit is given to the Mississippi State University Extension Service.

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