Pepper spot and scorch

Pepper spot and scorch, caused by the fungus Leptosphaerulina crassiasca, is a notable foliar disease affecting peanut crops globally. The pathogen belongs to the Ascomycota phylum and is known to compromise plant health by damaging photosynthetic tissue, particularly during the middle to late stages of crop development.

The disease manifests as small, dark, pepper-like spots on leaves, which may eventually coalesce into larger necrotic areas resembling scorched tissue. The edges of the lesions often feature a distinct yellow halo, indicating active colonization by the fungus. As the infection progresses, severe defoliation frequently occurs, weakening the host plant significantly.

The development of Leptosphaerulina crassiasca is strongly dependent on moisture and humidity. Frequent rainfall and prolonged leaf wetness provide ideal conditions for fungal sporulation and infection. The spores are typically dispersed by wind or splashing water, allowing the disease to spread rapidly throughout a field under favorable environmental conditions.

The economic impact of pepper spot and scorch is primarily driven by yield reduction. By reducing the leaf area available for photosynthesis, the disease restricts the plant's ability to fill the pods effectively. This leads to smaller peanut kernels and a reduced harvest weight, which necessitates timely intervention to maintain crop profitability.

Management strategies for controlling this disease include several essential agricultural practices:

• Crop rotation to reduce the load of inoculum present in the soil from previous seasons.
• Deep plowing to bury infested crop debris, limiting the survival of the fungus.
• Strategic application of foliar fungicides during peak humidity periods to protect the canopy.
• Selection of resistant or tolerant peanut varieties where such options are commercially available.