Phyllosticta leaf spot of cotton

Phyllosticta leaf spot is a fungal disease of cotton caused by the pathogen Phyllosticta gossypina. This disease primarily targets the foliage, resulting in the development of lesions that can severely compromise the plant's photosynthetic capacity and contribute to significant yield loss.

The disease affects cotton plants across various growth stages. The pathogen is highly opportunistic and thrives in environments where host tissues are readily accessible. Once established, the fungus can rapidly colonize leaves, leading to severe defoliation if left unchecked.

Visible symptoms include small, circular or irregular spots on the leaves. These spots typically start as light brown lesions with a darker border. As the infection progresses, the center of the spot becomes ashen and thin, eventually erupting with tiny, black, pimple-like fruiting bodies called pycnidia, which release spores.

The spread of Phyllosticta gossypina is highly dependent on environmental conditions, particularly high humidity and warm temperatures. These factors allow for the rapid germination of spores and their spread throughout the canopy via rain splashes and wind. The pathogen persists in crop residues, making field sanitation a critical component of control.

Managing this disease requires an integrated approach to ensure the health of the cotton crop:

• Removal and destruction of infected crop debris post-harvest.
• Implementation of crop rotation to break the infection cycle.
• Use of certified, disease-free seed and seed treatments.
• Application of systemic or contact fungicides when early symptoms are spotted.