Cotton anthracnose

Cotton anthracnose is a destructive fungal disease caused by the pathogen Colletotrichum gossypii. It is widely recognized as one of the major biotic threats to cotton production worldwide. The pathogen is known for its ability to persist in plant debris and soil, as well as being seed-borne, which allows it to initiate primary infection in new plantings easily.

The host range is primarily limited to the genus Gossypium. The disease affects cotton plants at all growth stages, posing a particular threat to young seedlings and developing bolls. If not managed properly, the fungus can rapidly colonize a field, causing significant yield losses and lowering the market value of the harvested fiber.

Symptoms of the infection typically appear as reddish or brown spots on leaves and stems. As the disease progresses, these spots develop into necrotic, sunken lesions. On the bolls, the disease presents as darkened, depressed areas that often develop a salmon-pink mass of fungal spores under humid environmental conditions, which is highly diagnostic for this disease.

The development and spread of Colletotrichum gossypii are heavily dependent on warm temperatures and high humidity. Frequent rainfall and overhead irrigation are major contributors to the rapid spread of conidia throughout the field. The pathogen thrives when daytime temperatures stay between 20°C and 28°C with prolonged leaf wetness.

The impact of cotton anthracnose is multi-faceted, ranging from seedling blight (damping-off) to the destruction of maturing bolls. Affected bolls may fail to open properly, leading to immature, discolored, and weak fiber. This ultimately affects the ginning process and the overall quality of the end-textile product, causing substantial economic setbacks for farmers.

Integrated disease management strategies are essential to minimize damage:

• Planting high-quality, certified, and treated seeds to eliminate primary inoculum.
• Implementing crop rotation cycles to break the survival chain of the fungus in the soil.
• Strict sanitation, including the destruction or deep incorporation of crop residues.
• Applying preventative fungicidal treatments during favorable weather conditions for disease development.
• Ensuring adequate plant spacing to improve air circulation and reduce humidity within the crop canopy.