Brown leaf spot of cassava

The causative agent of this disease is the fungus Passalora manihotis, historically documented as Cercospora henningsii. This pathogen belongs to the group of foliar fungi that primarily infect the leaves of cassava plants, significantly affecting the plant's overall physiology.

The primary host for this fungus is cassava (Manihot esculenta), a vital root crop in many tropical regions. The disease is widespread globally, often causing substantial economic losses in regions where environmental conditions favor the rapid proliferation of the pathogen throughout the growing season.

Symptoms initially appear as small, angular spots on the foliage that turn brown or tan with a distinct darker margin as the infection matures. In severe cases, these lesions coalesce, leading to chlorosis, necrosis of the leaf blade, and eventually premature defoliation of the entire plant.

Environmental factors such as high humidity, frequent rainfall, and warm temperatures create an optimal environment for the germination of fungal spores. The spread of the disease is predominantly mediated by wind and rain splashes, which facilitate the transport of conidia from infected to healthy plant tissues.

The economic impact of brown leaf spot is considerable, as defoliation reduces the photosynthetic capacity of the plant, directly limiting the development and storage of starch in the tubers. Effective management strategies include the use of disease-resistant varieties, maintaining adequate crop rotation, and strict field sanitation practices to eliminate inoculum sources.

• Use of certified, healthy planting material
• Field debris clearance after harvest
• Integrated pest management (IPM) practices
• Optimal plant spacing for air circulation