Chilli Cercospora Leaf Spot
· Capsicum & Chili
Also called frog-eye leaf spot. During the initial stage of an infection, brownish flecks with yellow margins appear on the leaves. Later on, they develop into large circular tan spots of up to 1.5 cm in size with dark rings growing around a whitish centre, resulting in the characteristic frog-eye appearance. These spots become more numerous on the leaf blade and slowly coalesce to form large lesions. The centers dry and drop out. At the final stage of infection, leaves turn yellow and wilt or drop.
The fungus survives in or on seeds and in the soil. Spores survive for one season in infected plant residue. Foliar infection occurs by direct penetration of the leaf and is favored by wet conditions. Optimal conditions for an infection are warm temperatures at 15-20°C and a relative humidity over 77%. The spores spread via water, rain, wind and via leaf to leaf contact.
Seed treatment with hot water at 52°C for 30 minutes is a way to reduce the presence on the fungus on seeds. Note that the treatment may also affect seed germination.
Always consider an integrated approach with preventive measures together with biological treatments if available. Seed treatment with captan 3g/kg works fine to fight the disease. Other treatmetns include foliar spray of copper hydroxide, carbendazim or mancozeb to control chilli cercospora leaf spot.