Cercospora leaf spot of pigeon pea

The fungus Mycovellosiella cajani, formerly known as Cercospora cajani, is the causal agent of leaf spot disease in pigeon pea (Cajanus cajan). This pathogen acts as a parasitic fungus that primarily attacks the foliage, severely limiting the photosynthetic capacity of the plant.

Pigeon pea is the primary host for this disease. The infection is particularly prevalent in tropical and subtropical regions where this crop is a staple. Both vegetative and reproductive stages of the plant are susceptible, leading to potential significant yield losses if left uncontrolled.

Symptoms typically begin as small, chlorotic spots on the upper leaf surface. As the infection progresses, these spots expand into brown or grayish necrotic lesions, often with a yellow halo. In advanced stages, the leaves may wither and drop prematurely, leading to severe defoliation of the canopy.

Disease development is highly dependent on environmental factors, specifically high humidity and temperatures between 20°C and 28°C. Rain splashes facilitate the spread of conidia from lower infected leaves to the upper canopy, while wind helps distribute the spores across the field.

To mitigate the impact of the disease, integrated pest management strategies are essential. These include crop rotation, the use of disease-free seeds, and the removal of infected crop debris. Chemical control using preventive fungicide sprays during the humid season is often required to maintain crop health and ensure optimal yields.