Anthracnose fruit rot
Colletotrichum acutatum (rarely C. fragariae and C. gloeosporioides)
Anthracnose fruit rot is a fungal disease that causes fruit rot and flower blight in warm wet weather. The pathogen is capable of infecting all above ground parts of the plant but these types of infection are less common.
Pink and red fruit develop light-brown lesions that eventually turn darker brown and sunken. Rotted areas of the fruit remain firm and dry. Pale orange to salmon colored spore masses cover the lesion during warm humid conditions. Ultimately the fruit dries down to a hard, black, shriveled mummy. Blossoms can be infected at any stage of development. Infected blossoms quickly die, dry out and turn brown. The brown discoloration often extends down the flower stalk.
The anthracnose fruit rot fungus is usually introduced to a site on infected planting material. Once established at the site the fungus overwinters on infected plants, plant debris and mummified fruit. Spores are produced in a sticky mass on any infected plant part during warm (68° F) wet weather. Anthracnose spores are spread by water via splashing or 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. The fungus has the ability to attack all plant parts, however fully open flowers and ripening fruit are most susceptible to the disease. Under warm, wet conditions, the fungus will produce spores on infected fruit which spread to neighboring plants resulting in new infections.
- There are no cultivars resistant to anthracnose fruit rot that are hardy in Minnesota.
- Purchase plants from a reputable supplier. Inspect all plants for symptoms of disease. Plant only healthy symptom free plants.
- Because spores are spread by splashing water, avoid the use of overhead irrigation and use drip irrigation or a soaker hose. If overhead irrigation cannot be avoided, water early in the morning on a sunny day to keep the time that the foliage is wet to a minimum.
- Maintain one to two inches of straw mulch between the rows or walking alleys to reduce splash dispersal of disease spores.
- Remove infected berries from the planting during harvest to reduce spread of the disease to developing fruit.
If anthracnose has been a problem in the past and weather is warm and wet during flowering and fruit production, fungicides can be applied to reduce infection. Anthracnose is not easily controlled by fungicides and gardeners should expect a reduction in disease but not complete protection. Fungicides with Copper, Captan or Bacillus subtilis listed as the active ingredient provide some protection from anthracnose fruit rot. All label instructions must be read and followed when applying a pesticide.