Web blotch of peanut

Web blotch is a fungal disease affecting peanut plants (Arachis hypogaea), caused by the pathogen Didymosphaeria arachidicola. It is recognized as a significant foliar disease that can impact yields, particularly in humid tropical and subtropical growing regions.

The primary host for this pathogen is the peanut crop. The disease targets the leaves, causing structural damage to the leaf tissue, which inhibits photosynthesis and interferes with the plant's ability to allocate nutrients to the developing pods underground.

Clinical signs of the infection include the development of irregular, brown-to-dark spots on the leaflets. As the infection progresses, these spots often exhibit a distinct web-like or reticulated pattern of necrotic tissue. In severe cases, the lesions coalesce, leading to premature defoliation and a drastic reduction in the plant's canopy.

The pathogen thrives in environments characterized by high humidity, frequent rainfall, and warm temperatures. These conditions facilitate the release and dispersal of spores, which are often spread by wind and rain splashes. The fungus overwinters on debris left in the field from the previous season, acting as a primary reservoir for the next crop.

Integrated management is essential for controlling web blotch. Key strategies include:

• rotation with non-host crops to break the disease cycle
• deep plowing to bury infected plant residues
• application of preventative and curative fungicides
• maintaining good crop nutrition to improve overall plant vigor