COTTON :: MAJOR DISEASE :: BOLL ROT

Boll rot - Fungal complex
It is a complex disease caused by several fungal pathogens viz., Fusarium moniliforme, Colletotrichum capsici, Aspergillus flavus, A. niger, Rhizopus nigricans, Nematospora nagpuri and Botryodiplodia sp.
Symptoms

Initially, the disease appears as small brown or black dots which later enlarge to cover the entire bolls. Infection spreads to inner tissues and rotting of seeds and lint occur. The bolls never burst open and fall off and prematurely. In some cases, the rotting may be external, causing rotting of the pericarp leaving the internal tissues free. On the affected bolls, a large number of fruiting bodies of fungi are observed depending upon the nature of the fungi involved

Favourable Conditions

• Heavy rainfall during the square and boll formation stage,
• Wounds caused by the insects,
• Especially red cotton bug Dysdercus cingulata
• Close spacing and excessive nitrogen application.

Disease Cycle
The fungi survive in the infected bolls in the soil. The insects mainly help in the spread of the disease. The fungi make their entry only through wounds caused by the insects. The secondary spread of the disease is also through air-borne conidia.
Management

• Adopt optimum spacing.
• Apply the recommended doses of fertilizers.
• Spray Copper oxychloride 2.5kg along with an insecticide for bollworm from 45th day at 15 days interval.
• Two or three sprays are necessary.