Web Blotch
(Phoma arachidicola)

Web blotch was first found in the North Carolina-Virginia region in September 1979. Initially leaf lesions are visible only on the upper surface of leaves. As the disease progresses, brown to dark brown or almost black blotches develop. Web or net-like lesions may develop under some environmental conditions or they may occur simultaneously with blotch symptoms. When several lesions develop on individual leaves, heavy defoliation of plants will result. The web blotch fungus can survive from season to season in crop residue.



Both the irregular shape of lesions and the failure of lesions to show on the lower leaf surface until final stages of disease aid in distinguishing this disease from early and late leafspot. Web blotch also differs from Cercospora leafspot in that web blotch development requires longer periods of leaf wetness and cooler temperatures.