Cotton anthracnose

Systematic position and nature of the pathogen: Glomerella gossypii (the teleomorph of Colletotrichum gossypii) is an ascomycete fungus classified within the order Phyllachorales. It is a severe phytopathogen responsible for cotton anthracnose, a disease that significantly impacts cotton production worldwide. The pathogen is known for its ability to attack the host at any growth stage, from seed germination to boll maturation.

Diseases and host crops: The primary host for this pathogen is the cotton plant (Gossypium). The disease symptoms include seedling blight, leaf spots, stem lesions, and boll rot. Seed infection often leads to poor emergence and seedling death, while the infection of mature bolls destroys the lint quality, causing significant financial losses for farmers during harvest.

Biology and life cycle: The life cycle of this fungus involves both asexual (conidial) and sexual (perithecia producing ascospores) reproduction. The pathogen survives in infested crop debris and on seeds. During the growing season, conidia are disseminated primarily by rain splash, wind, and insect vectors. The fungus enters the plant tissues through stomata or mechanical injuries and spreads mycelia throughout the host tissue.

Conditions for development and spread: Glomerella gossypii thrives in environments characterized by high humidity (above 85%) and moderate temperatures ranging from 20°C to 28°C. Persistent rainfall during the flowering and boll-setting stages creates optimal conditions for rapid disease spread. Poor field management, such as high planting density and lack of drainage, further exacerbates the proliferation of the fungus.

Damage and control measures: The economic impact is severe due to stand loss and the degradation of cotton fiber. Effective management strategies include:

• Using high-quality, certified, and fungicide-treated seeds.
• Implementing rigorous crop rotation practices to break the disease cycle.
• Practicing deep plowing to bury crop debris and eliminate overwintering sites.
• Applying preventive and curative fungicides when environmental conditions favor disease development.