Late leaf spot of peanut

Nothopassalora personata is the fungal pathogen responsible for the late leaf spot disease in peanuts (Arachis hypogaea). This disease is considered one of the most destructive foliar infections affecting peanut production worldwide, often causing substantial yield losses if management practices are neglected during the critical growth stages.

The fungus primarily attacks peanut plants, affecting leaves, petioles, and stems. The initial symptoms appear as small, dark spots on the lower leaf surface, which gradually enlarge into circular, dark brown to black lesions. Unlike early leaf spot, these lesions are darker in color and often lack the prominent yellow halo associated with other pathogens.

As the infection progresses, severe necrosis occurs, leading to extensive defoliation. The loss of leaf area directly impacts the plant's photosynthetic capacity, resulting in reduced kernel weight, poor seed quality, and significant harvest losses. In severe cases, premature leaf drop can expose the soil and lead to further developmental issues for the pegs.

The disease thrives in environments characterized by high humidity and warm temperatures, typically between 20°C and 30°C. The pathogen produces conidia that are disseminated through rain splash, wind, and irrigation water. The fungus persists in the soil and on crop debris, making survival over the winter months highly efficient in warm climates.

Managing late leaf spot requires a multi-faceted approach. Preventive measures include:

• Planting resistant or tolerant peanut varieties.
• Implementing strict crop rotation schedules to break the pathogen's life cycle.
• Sanitation practices, such as burying crop residues after harvest.
• Applying protective and systemic fungicides during the growing season when environmental conditions favor disease spread.