Yam anthracnose

Colletotrichum alatae is a pathogenic fungus responsible for the devastating yam anthracnose. As a serious phytopathological threat, it significantly impacts the production of edible yams, specifically Dioscorea alata, causing substantial harvest losses worldwide in tropical agricultural regions.

The fungus affects various parts of the yam plant, primarily leaves, petioles, and stems. In severe cases, the infection spreads to the tubers, leading to post-harvest decay. The reduction in photosynthetic leaf area due to the lesions directly inhibits tuber development and reduces the overall yield potential of the crop.

Early symptoms appear as small, water-soaked, dark-brown or black spots on the leaves. As the disease progresses, these spots expand, often surrounded by a chlorotic halo. Under high humidity, salmon-colored spore masses may become visible on the necrotic tissue. Severe infections lead to shoot blight, leaf drop, and in extreme cases, the total collapse of the plant canopy.

The development of Colletotrichum alatae is highly dependent on environmental conditions, particularly prolonged periods of high humidity, heavy rainfall, and warm temperatures. These factors stimulate spore production and dispersal, which occurs through rain splash and wind-borne movement, facilitating rapid transmission across the field.

Effective management requires an integrated pest management (IPM) strategy. Key practices include:

• planting resistant or tolerant yam varieties;
• the use of certified disease-free planting material;
• proper spacing to ensure good air circulation and lower canopy humidity;
• sanitation measures, such as the removal and destruction of crop debris;
• strategic application of protective fungicides during the onset of the rainy season.