COTTON :: MAJOR DISEASE :: ANTHRACNOSE

Anthracnose - Colletotrichum capsici
Symptoms
The pathogen infects the seedlings and produces small reddish circular spots on the cotyledons and primary leaves. The lesions develop on the collar region, stem may be girdled, causing seedling to wilt and die. In mature plants, the fungus attacks the stem, leading to stem splitting and shredding of bark. The most common symptom is boll spotting. Small water soaked, circular, reddish brown depressed spots appear on the bolls. The lint is stained to yellow or brown, becomes a solid brittle mass of fibre. The infected bolls cease to grow and burst and dry up prematurely.

Pathogen
The pathogen forms large number of acervuli on the infected parts. The conidiophores are slightly curved, short, and club shaped. The conidia are hyaline and falcate, borne single on the conidiophores. Numerous black coloured and thick walled setae are also produced in acervulus.
Favourable Conditions

• Prolonged rainfall at the time of boll formation
• Close planting.

Disease Cycle
The pathogen survives as dormant mycelium in the seed or as conidia on the Surface of seeds for about a year. The pathogen also perpetuates on the rotten bolls and other plant debris in the soil. The secondary spread is by air-borne conidia. The pathogen also survives in the weed hosts viz., Aristolachia bractiataand Hibiscus diversifolius.
Management

• Treat the delinted seeds with Carbendazim or Carboxin or Thiram or Captan at 2g/kg.
• Remove and burn the infected plant debris and bolls in the soil.
• Rogue out the weed hosts.
• Spray the crop at boll formation stage with Mancozeb 2kg or Copper oxychloride 2.5 kg or or Carbendazim 500g/ha.