The low yield of Cotton in our country is due to crop diseases, insects and nutrients deficiency.
Important diseases are root rot, wilt, leaf spot, grey mildew, rust, anthracnose, bacterial leaf blight, leaf curl and tobacco streak virus.Different stages
These diseases occur almost regularly at different stages of the growth and cause heavy damage. Tobacco Streak virus is the most destructive.
Initially brickish red necrotic spots appear on the young leaves, spreading lesions on leaves, sometimes forming numerous diffuse ring spots.
Slowly the area of discoloration increases and the leaf may turn reddish and dry up completely. Infected leaves show alternating light green and red patches.
Bud and flower production get reduced. Infected plants mature late and are small in size. Early infection causes death of the plant before flower or bud set.
Diseased plants exhibit leaf curling and mosaic with stunted growth. Infection causes reduction in plant yield and quality of bolls. This disease is transmitted by thrips.Management strategies
Seed dressing with appropriate insecticide before sowing should be done.
Follow crop rotation and field sanitation. Grow suitable region-wise resistant varieties.
Remove affected leaves/plants from crop fields to avoid secondary spread.
Destroy host weeds such as parthenium, tridax and other weeds around the cotton crop, which will help limit the occurrence of this disease.
Inter crop with short duration non-host crops like sorghum, redgram, greengram, blackgram soyabean, pearl millet and maize.
Spray insecticides such as methyl demeton at 2.0 ml or thiomethoxam at 0.2 gm or monocrotophos at 1.6 ml or acetamiprid at 0.2 gm or acephate 1.5 gm /l at the initial stage of disease. Foliar sprays of Fipronil at 2ml/l also control the vector spread.
Barrier crop such as sorghum, maize etc., can be grown in 3 to 4 rows.
(Dr. Vijaya Bhaskar Rao is Scientist (Plant Pathology), email :email@example.com, mobile: 098498 17896, Regional Agricultural Research Station ,Warangal and Professor Jayasankar is from Telangana State Agricultural University, Hyderabad, Telangana.)