Sesame cercospora leaf spot

Sesame cercospora leaf spot is a significant fungal disease affecting sesame production globally, caused by the pathogen Pseudocercospora sesami. This disease is categorized as a foliage blight that specifically targets members of the Sesamum genus, often leading to yield losses in both seed quality and quantity.

The fungus infects various parts of the plant, including leaves, stems, and seed capsules. While the disease can manifest at various growth stages, it is most prevalent during the reproductive phase of the crop. Once established, the pathogen produces conidia that are disseminated by wind and splashing rain to healthy plant tissues.

Symptoms initially appear as small, chlorotic to brown circular or irregular spots on the leaf blades. As the infection progresses, these spots enlarge, turn necrotic, and may coalesce to form large blighted areas. Under humid conditions, a fuzzy greyish appearance of the fungus becomes visible on the underside of the leaves, followed by defoliation.

Environmental conditions play a critical role in the epidemiology of the disease. High relative humidity and warm temperatures, typically between 25°C and 30°C, are ideal for the rapid germination of spores and the secondary spread of the infection. The pathogen can survive for extended periods in infected plant debris left in the field.

Effective management requires an integrated approach to minimize fungal inoculum pressure. Key strategies include the use of disease-resistant varieties where available, crop rotation cycles to break the disease life cycle, and the destruction of crop residues. Fungicidal treatments should be applied preventatively or upon the first appearance of symptoms to protect the canopy.