Pepper spot

Pepper spot is a fungal disease affecting peanut crops (Arachis hypogaea), caused by the pathogen Leptosphaerulina arachidicola. This disease is recognized globally as a significant factor in yield reduction due to the destruction of the plant's photosynthetic surface area.

The causal agent is an ascomycete fungus that survives in infected crop debris on or in the soil. During the growing season, the pathogen produces conidia, which are disseminated to healthy leaves primarily through splashing rain and wind currents, initiating primary and secondary infection cycles.

The initial symptoms are characterized by small, distinct, dark brown to black spots on the leaves. As the disease progresses, these spots may coalesce into larger, irregular necrotic areas. In severe cases, extensive defoliation occurs, which compromises the plant's ability to develop pods and seeds effectively.

Environmental conditions that favor the development and spread of Leptosphaerulina arachidicola include high humidity, prolonged leaf wetness, and moderate temperatures. Dense crop canopies that limit air circulation are particularly susceptible to rapid disease development, as they retain moisture needed for fungal growth.

Management of Pepper spot requires an integrated approach to maintain crop health. Effective strategies include practicing crop rotation to reduce inoculum pressure, deep plowing to bury infested residue, and the timely application of systemic or contact fungicides during periods of high disease risk to minimize crop damage.