Strawberries With Anthracnose – Treating Strawberry Anthracnose Disease

Strawberries With Anthracnose – Treating Strawberry Anthracnose Disease

By: Mary H. Dyer, Credentialed Garden Writer

Anthracnose of strawberries is a destructive fungal disease that if left uncontrolled, can decimate entire crops. Treating strawberry anthracnose may not eliminate the disease entirely, but early attention can keep the problem in check.

Strawberry Anthracnose Information

Anthracnose of strawberries was once thought to be a disease of warm, humid climates, but the problem is becoming more widespread wherever strawberries are grown.

The disease is usually introduced on infected strawberry plants. Once established, the fungus can live in the soil for several months. The fungus overwinters on dead leaves and other plant debris, and is harbored by several types of weeds.

Although the spores aren’t airborne, they are distributed by splashing rain, irrigation, or by people or garden tools. Anthracnose of strawberries develops and spreads very quickly.

Signs of Strawberries with Anthracnose

Anthracnose of strawberries attacks nearly every part of the strawberry plant. If the crown of the plant is infected, usually showing rotted, cinnamon-red tissue, the entire strawberry plant may wilt and die.

On fruit, signs of disease include pale brown, tan or whitish lesions. The sunken lesions, eventually covered by pinkish-orange spores, enlarge quickly to cover entire berries, which may gradually become black and mummified.

Flowers, leaves and stems may also display tiny masses of salmon-colored spores.

How to Treat Strawberry Anthracnose

Plant only disease-resistant cultivars. Be sure plants are healthy and disease-free when you bring them home from the nursery. Check your strawberry patch frequently, especially during warm, wet weather. Remove and destroy diseased plants as soon as they appear.

Water at ground level whenever possible. If you must use sprinklers, water in the morning so the plants have time to dry before temperatures drop in evening. Don’t work in the strawberry patch when plants are wet. Mulch the planting area with straw to help minimize splashing water.

Avoid overfeeding, as too much fertilizer can make strawberry plants more susceptible to disease.

Remove old, infected plant debris, but be careful about working in the area when infections are present. Keep garden tools clean to prevent spread of disease to non-infected areas. Keep weeds in check, as certain weeds harbor the pathogen that causes strawberries with anthracnose.

Practice crop rotation. Don’t plant strawberries or other susceptible plants in an infected area for at least two years.

Fungicides may be useful if applied at the first sign of disease. Your local cooperative extension office can provide specifics about use of fungicides in your area.

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Read more about Strawberry Plants

Home Garden Strawberries

G. W. Krewer and Marco Fonseca, Former Extension Horticulturists
Phil Brannen, Extension Plant Pathologist

Reviewed by Robert Westerfield

To get a strawberry bed started, all you need is a small area that receives full sun most or all day. Strawberries will grow well in many types of soil, but the most desirable soil is fertile, medium-light in texture, well drained and with good moisture-holding capacity. Avoid heavy clays, deep sands and wet soils.

After selecting the site, have the soil tested to determine lime and fertilizer needs. Also, have the soil assayed for nematodes. Your county extension office has information and supplies for making tests. If lime and/or other nutrients are needed, or nematode treatment is recommended, don't neglect to do as suggested these treatments are essential to produce good berries.

Because of diseases, two very different production systems are used in Georgia. In the matted row system, plants are set out one spring and fruit the next. This system works best in north Georgia, and production may continue for several years. In the annual hill system, plants are set out in the fall and fruit the next spring. The planting is usually destroyed after the crop is harvested. This system works best in middle and south Georgia.

Anthracnose on strawberries

This disease has been observed sporadically on Long Island, reflecting the fact the pathogen is not widespread and conditions are not always favorable. A combination of high temperature (80 F is optimum), the most important factor, and wet plant tissue are needed for anthracnose to develop. Conditions evidently were favorable during spring in 2010, 2012, 2018 and 2019. Symptoms were first seen from mid May to early June those years by Cornell Cooperative Extension IPM scouts. Spores of the pathogen are dispersed by splashing water. Humidity near 100% is needed for infection. Spores are produced abundantly and disease development is rapid under favorable conditions. Consequently crops can quickly become severely affected.

The primary symptom is fruit rot. These start to form on ripening fruit as small, white to light brown, water-soaked spots that typically enlarge quickly, becoming dark brown to black, slightly sunken, and can consume the entire fruit. Green fruit can also develop spots that are very small, being restricted to individual seeds, which turn black. Symptoms also develop on crowns, leaves, flowers, pedicels and peduncles. Infected crown tissue can result in plants wilting and dying.

Symptoms are often associated with a specific variety, which is not because of greater susceptibility, but rather reflects the fact the pathogen was present on these plants when purchased. Infected transplants and contaminated soil are the main sources of the pathogen. It can be present without causing symptoms. Indexing is not done for this pathogen.

Successfully harvesting from an infested planting can be difficult because symptoms can develop quickly after harvest. As much as 25% of fruit could start to rot in just 1 day! Unfortunately anthracnose is very difficult to control when conditions are favorable during harvest, especially when management practices were not implemented earlier.

The pathogen can survive between seasons in soil or infested plant debris, especially mummified fruit. Starting with anthracnose-free plants is a key management practice. Sweet Charlie is an early variety with resistance. High levels of nitrogen favor anthracnose development, therefore using minimal fertilizer is recommended where the pathogen is established. Minimize pathogen dispersal by using straw mulch, at least between rows, and drip irrigation. Plastic mulch between rows has been shown to increase splash dispersal of the pathogen. The pathogen can also be moved by workers or on equipment, therefore affected fields should be worked in last.

For commercial growers, strobilurin fungicides (Abound, Cabrio, Pristine) currently are the most effective option for anthracnose. They can only be applied twice before a different class of fungicide must be used. Switch is the best choice for alternating. Captan, Captevate, and Thiram are good protectant fungicides for early in the season.

Below: Salmon-colored masses of spores are diagnostic for the fungus causing anthracnose. They are evident upon close examination of the first photograph below taken the day fruit was picked. They are more evident in the second photograph of the fruit after it incubated on wet paper towel in a closed plastic bag for a day, which is a useful diagnostic method. These photographs of the same fruit also illustrate how quickly symptoms of anthracnose fruit rot can develop.

Please Note: The specific directions on pesticide labels must be adhered to — they supersede these recommendations, if there is a conflict. Any reference to commercial products, trade or brand names is for information only no endorsement is intended. For up-to-date information on labeled fungicides see Cornell Integrated Crop and Pest Management Guidelines for Commercial Vegetable Production

Fruit Rot Identification and Prevention

Verticillium Wilt

Verticillium wilt is a serious fungal disease of the soil that occurs if strawberries are planted near other plants known to harbor the disease. Common plants that harbor the disease include eggplants, potatoes, tomatoes, and peppers.

Prevention Tip: Be careful where you plant.

Verticillium wilt infestation.

Strawberry Gray Mold

Strawberry gray mold is caused by the Botrytis cinerea fungus and is the most serious and common form of strawberry fruit rot. The disease can reduce your yield by 50 percent or more. The mold flourishes during long periods of rain and overcast conditions during bloom time and harvest. Strawberry infections generally appear on the fruit as a light-brown patch that quickly enlarges and decays. With moist conditions, the fluffy fungal growth is visible on the infected tissue. The gray-brown color gives the disease its name.

Prevention Tip: Better air flow and improved sunlight penetration will help reduce the possibility of gray mold. This is readily achieved by thinning out the strawberry beds. During the winter, dead leaves and debris should be removed from the beds to reduce possible sources of fungus.

Anthracnose Fruit Rot

Anthracnose fruit rot, caused by Colletotrichum acutatum, is a destructive disease affecting California cultivars if they grow on black plastic. The practice, most destructive during warm weather, can cause between 60 to 75 percent of fruit loss. Anthracnose fruit rot appears on green strawberries and ranges in appearance from soft to firm brown or black spots. On ripe fruit, the disease appears as purple spots and enlarges quickly until the whole strawberry rots. Pink lesions on the surface can turn to masses of orange spores. Spores are dispersed to other fruit in splashing water. You may think this is a convenient way to prevent weeds but it should be entirely avoided.

Prevention Tip: Do not use black plastic for weed control.