Strawberry Anthracnose is a deadly disease of strawberry with all parts of the plant (fruit, crowns, leaves, petioles and runners) being susceptible to the pathogen.
Three related species of the fungus Colletotrichum, including C. acutatum, C. gloeosporioides, and C. fragariae are associated with the disease. However, C. acutatum is the main species.
Strawberry Anthracnose Cycle
The primary source of anthracnose inoculum enters the fields on strawberry transplants.
The pathogen can grow in green tissue, even without showing any symptoms, then remain inactive or even produce spores. When the green tissue dies, the fungus becomes active and can produce many spores. C. acutatum can survive in soil and on infected plants and plant debris, such as old dead leaves and mummified fruit, and may infect weeds growing alongside of the field.
Spore production, germination, and infection are favored by warm, humid weather and rainfall. The spores are spread by splashing rain, wind-driven rain, and by people or equipment moving through the field. They are not airborne so they do not spread over long distances in the wind.
Spores require free water on the plant surface in order to germinate and initiate infections and disease development can occur very rapidly, with up to 90% of the fruits getting infected within a week or less.
Signs and Symptoms of Strawberry Anthracnose
The fungus can attack fruit, runners, petioles, and the crown of the plant.
Dark elongated lesions develop on petioles and runner stems. Affected petioles and stems are sometimes girdled by lesions, causing individual leaves or entire daughter plants to wilt and die. Under warm, humid conditions, salmon-colored masses of spores may form on the lesion surface.
Infected flowers may die and dry out and if infection occurs shortly after pollination, the developing fruit remains small, hard, and misshapened.
If the crown tissue is infected, crown rot may develop and the entire plant may wilt and die. When these infected crowns are sectioned, internal tissue is firm and reddish-brown to dark-brown in color. Crown tissue may be uniformly discolored or streaked with brown.
Whitish, tan, or light-brown water-soaked lesions develop on fruit. These lesions eventually turn brown or dark-brown, become sunken, and enlarge within two to three days to cover most of the fruit. The lesions are covered with pale-orange or salmon-colored spore masses. Under moist conditions, the fungus may grow out around the edge of the lesion or through the lesion, giving a fuzzy appearance. Infected fruit eventually dry down to form hard, black, shriveled mummies. Fruits can be infected at any stage of development.
The pathogen can also wash down into the root zone and cause black lesions on roots. Infected tips can lead to widespread infections on young tissue of the plug plants and plant loss.
Strawberry Anthracnose Management
The following fungicides are recommended for prevention and eradication of strawberry anthracnose disease.
- Use disease-free planting material.
- Plant resistant varieties
- Avoid the use of overhead irrigation and use drip irrigation if possible in order to keep the crop dry.
- Mulching with straw reduces water splash and disease spread.
- Remove infected plant parts as they serve as a source of inoculum for the disease.
- To avoid spreading the disease, keep out of gardens when plants are wet and make sure to disinfect all garden tools after use.
- Do not compost infected plants or plant parts and thoroughly clean up garden areas in the fall, after harvest, to reduce over wintering sites for the fungal spores.
- Ensure proper spacing to facilitate free air movement within the crop
- Fungicides should be mixed with INTEGRA 3ml/20l, which improves the efficacy of the fungicide by acting as a sticker, spreader, wetter and penetrant.
- Alternating different fungicides throughout a plant’s season prevents the fungus from developing resistance over any of the fungicides.
- Timely control of the diseases is very critical.
- A proper nutrition keeps activates the crop’s defense system against infections.