Leaf Spot
Septoria spp., Cercospora spp., Alternaria spp., Phyllosticta spp., Bipolaris spp.
Overview
A general term for various fungal and bacterial diseases that cause discrete spots or lesions on leaves. Spots may be circular, angular, or irregular, and often have distinct borders or halos.
Symptoms
Circular to irregular spots on leaves, often with tan, brown, or dark centers and distinct margins. Spots may coalesce, causing large areas of dead tissue. Premature defoliation in severe cases.
Environmental Conditions
Humid
Prevention
Ensure adequate spacing for air circulation. Avoid overhead watering. Remove fallen leaves and debris. Rotate crops. Use disease-free seed and transplants.
Management
Apply copper-based or broad-spectrum fungicides. Remove severely infected leaves. Improve air circulation through pruning. Mulch to prevent soil splash onto lower leaves.