A newly-emerging disease, caused by Tobacco Streak Virus(TSV) and affecting the BT cotton crop, is creating panic among farmers in Kurnool and Nandyal districts, where pink bollworm is already wreaking havoc causing severe yield loss.
The BT cotton, grown in 4 hectares, is one of the major crops in the undivided district of Kurnool. The Tobacco Streak Virus is affecting approximately 10% to 15% of the total cropped area of cotton in Kurnool.
“At present, the incidence is concentrated in Gudur, Kodumuru, Emmiganur madals of Kurnool district and Atmakur and Nandyal mandals of Nandyal district,” said scientists of Regional Agricultural Research Station(RARS), Nandyal.
Prolonged dry spells during the initial growth phase favours rapid multiplication of sucking pests like thrips, which is the carrier of the TSV virus, RARS Associate Director of Research N.C. Venkateswrlu and entomologist Sivarama Krishna told The Hindu.
The symptoms of TSV include appearance of brickish-red necrotic spots on the young leaves initially, spreading lesions on leaves, and sometimes forming numerous diffusing ring spots. Slowly, the area of discoloration increases and the leaf turns red and can dry up completely. Infected leaves show alternating light green and red patches.
Bud and flower production gets reduced. Infected plants mature late and are small in size. The early infection causes the death of the plant before the flowering or bud sets in. The affected plants show leaf curling and mosaic with stunted growth.
The affected leaves/plants must be removed from fields to avoid secondary spread.
The host weeds like parthenium, tridax, and others must be destroyed, the scientists said, urging farmers to go for intercropping with short-duration non-host crops like sorghum, redgram, green gram, black gram soya bean, pearl millet, and maize to stop the spread of the disease.