Bacterial leaf blight in cotton — identify it early, treat it right
Spot the early signs, choose the right copper-based spray, and break the cycle next season. A practical Khetiyaar field guide.
Catch it in week one and ₹500 of copper spray saves the crop. Catch it in week three and you're rebuilding plant population.
How it looks — early vs late
Early: small, water-soaked, angular yellow patches between leaf veins, usually on lower leaves. Press the leaf back-to-light — patches look translucent. This is the moment to act.
Late: spots brown out, merge into blotches, leaves drop. Bacteria moves to bolls — black sunken spots, lint quality crashes. Once you see this, save what you can; protect the rest.
Treatment that works
Spray copper oxychloride (3 g/L) at sunset — never midday, the heat damages leaves. Repeat at 7-day intervals, 3 sprays max. Add streptocycline (50 ppm) for the second spray if it's spreading.
Cut all infected lower leaves, burn (don't compost) them. Stop overhead irrigation for 5 days — bacteria love wet foliage.
Prevent next season
Treat seed with hot water (50°C, 20 minutes) before sowing. Rotate cotton with cereals or pulses for at least one season. Keep field trash burned or composted hot — bacteria overwinter in residue.
Choose tolerant varieties on plots that flooded last year. Khetiyaar's planner suggests these by district.
