Cotton is one of the most important cash crops of the world, and it is grown on a large scale in many countries. However, the crop is susceptible to various diseases, and one of the most devastating diseases of cotton is alternaria blight.
Alternaria blight is caused by the fungus Alternaria alternata, which commonly attacks cotton plants during the flowering and boll-forming stages of growth. The disease affects the leaves, stems, flowers, and bolls of the plant, and it can result in significant yield losses.
Symptoms of alternaria blight include small, dark-brown to black circular spots on leaves, which may elongate and coalesce to form large necrotic areas. The fungus causes premature defoliation of the cotton plant, reducing the boll size and weight, and ultimately leading to yield losses.
Control measures for alternaria blight in cotton include the use of cultural and chemical methods. Cultural methods include rotation of crops, using resistant cotton varieties, practicing good sanitation, and reducing irrigation during flowering and boll development.
Chemical control measures involve the use of fungicides to control the disease. Fungicides such as azoxystrobin, tebuconazole, and trifloxystrobin are effective in controlling the disease. However, their use should be as per recommendations provided by the extension unit or department of concerned authorities.
The effective control of alternaria blight in cotton involves an integrated pest management approach, involving a combination of cultural and chemical methods. The use of resistant cultivars and good cultural practices can significantly reduce the incidence and severity of the disease. In addition, timely application of fungicides when warranted can prevent significant yield losses.
It is recommended that farmers monitor their cotton fields regularly for the appearance of the disease and take appropriate measures to control it promptly. Early detection and management are critical in controlling the spread of alternaria blight in cotton.