Cercospora leaf spot

Small circular necrotic spots (lesions) usually appear on older leaves. These spots join up causing leaf blight and leaf drop. The African isolates of the fungus produce concentric areas on the leaf spots. The disease causes severe losses when defoliation occurs before flowering and podding. The disease usually appears when plants are flowering and podding. The fungus is seed-borne. It is favoured by cool temperatures (25 degC) and humid rainy weather. The disease is more common in the long-duration and perennial varieties in Eastern Africa.