Sooty blotch is one of the most common diseases of apples in the Southeast.
The fungi causing the disease affect all apple cultivars. Sooty blotch fungi only grow on the surface of the fruit, giving it an unsightly appearance. The fungal colonies are olive green to black on mature fruit. Colonies can be round or feathery, have diffuse margins and cover the entire fruit, says Edward Sikora, Extension plant pathologist with the Alabama Cooperative Extension System. The complex of fungi that cause sooty blotch grows on the waxy cuticle of the apple fruit.