ICAR-NOFRI 07/03/19

Alternaria leaf spot symptoms first appear as greenish brown, water-soaked lesions. Lesions quickly become dark brown to black with or without yellow halos. Under disease-favorable conditions, lesions coalesce and cause entire leaves to become yellow, collapse, and die. Older leaves are most susceptible to infection and often the first to develop symptoms, but all leaves can be infected. Petiole lesions appear similar to leaf lesions, but are more elongated; petiole lesions quickly kill entire leaves. Disease symptoms are often confused with Cercospora leaf spot and bacterial blight, and microscopic examination is often necessary for accurate diagnosis and its causal organism is Alternaria brassicicola .