1. Twig and Stem Blight of Cotton
- Dieback initiating from the twigs with multiple lesions coalescing together on the stem, resulting in the death of the branches.
- Abundant, black, and solitary pycnidia were observed on symptomatic twigs.
- Seed treatment is a pre-requisite.
- Should maintain plant to plant and row to row distance.
- Should properly irrigate the field. Avoid excessive irrigation as it increases humidity that favors fungal growth.
- Use protectant spray if a favorable environment prevails for more than two days.
- Always keep in mind the wind direction while spraying the field.
- Spray the plant from head to bottom.
- Following fungicides could be sprayed.
Amistar Top 325 SC (Azoxystrobin + Difenoconazole) @ 2.0 cc/lit of water.
Nativo 75% WG (Tebuconazole + trifloxystrobin) 1g//lit of water
Score 250EC (Difenoconizole) @ 1cc/lit of water
2. Asochyta blight
- Brown or gray spots on leaves surrounded by a red halo;
- Elongated red-purple cankers on stems cause the wilting and death of leaves above.
- No fungicides are currently registered for use in cotton.
- Plough the crop debris into the soil after harvest.
- Crop rotation has little to no effect on control of the disease.
3. Cercospora leaf spot
- Circular red lesions on leaves which enlarge and turn white or gray in the center
- Lesions often have a pattern of concentric rings and possess a red margin
- Dark gray spore masses form in the centers of the lesions making them appear dark gray.
- Plough the crop residue into the soil to reduce inoculum levels
- Provide plants with adequate irrigation and nutrients
- Applications of appropriate foliar fungicides may be required on susceptible cultivars.
4. Fusarium wilt
- Wilting of cotyledons and seedling leaves
- Cotyledons become chlorotic at the edges and then necrotic
- Older plants exhibit symptoms of wilting and leaf chlorosis
- Wilting is usually gradual but may be pronounced after a heavy summer rain
- If the infection is severe plants become stunted and may be killed
- The vascular system of infected plants becomes discolored and can be seen by cutting the stem.
- Use the certified, disease-free seed
- Plant varieties with higher resistance to the disease in areas with a history of Fusarium diseases
- Fumigating the soil may reduce disease incidence.
5. Bacterial Blight of Cotton
- Attacks on all above-ground parts.
- Spots on under the surface of cotyledons.
- On leaves, water-soaked spots firstly on the lower surface and then appear on both surfaces of the leaf.
- Increase in size of spot and yellowing.
- Vein blight.
- Water-soaked lesions on bolls
- Remove and destroy the plant debris.
- Use resistant varieties.
- Use acid delinted seeds.
- Treat the seed with a bacteriocide.
- Hot water treatment of seed at 56 oC for 10 minutes.
6. Cotton Leaf Curl Virus
- Leaf curling
- Darkened veins
- Vein swelling
- Cup-shaped leaf enation
- The intensity of CLCuVD varies from locality to locality
- Vector control reduces CLCuVD infestation
- Seed dressing insecticides, yellow sticky traps, Adulticides / Nymphicides are effective tools to suppress whitefly.
- Resistant variety is the best solution