Bollworm Control — How to Identify, Treat & Prevent Bollworm in Your Crop
Bollworm is one of the most damaging pests in Indian cotton and vegetable cultivation, boring into fruits and bolls to cause direct yield loss. Pheromone trap monitoring and timely diamide sprays are the most effective control strategy.
How to identify bollworm
Watch for these signs in your field.
Entry holes in bolls and fruits with frass
Round entry holes on bolls or fruits with frass (caterpillar excreta) at the opening — the first visible sign of active bollworm feeding inside.
Withered and dropped squares and bolls
Young squares and small bolls wither and drop prematurely as the larva feeds inside, causing severe yield loss in heavy infestations.
Tunnelling damage inside fruit
Cross-section of damaged fruit shows tunnelled, hollowed-out interior. Larva feeds and exits, leaving the fruit rotten and unmarketable.
How to control bollworm
Follow this step-by-step protocol for best results.
Monitor with pheromone traps
Install Helicoverpa armigera pheromone traps at 5 per acre. Spray when trap catches exceed 8 moths per trap per week (Economic Threshold Level). Monitoring prevents unnecessary sprays and helps time treatments accurately.
Apply a diamide or macrolide insecticide
Use Chlorantraniliprole 18.5% SC (0.3 ml/L) or Emamectin Benzoate 5% SG (0.4 g/L) for reliable control. These molecules penetrate plant tissue and kill larvae feeding inside. Spray in the evening when larvae are most active.
Rotate chemistry to prevent resistance
Bollworm is notorious for developing insecticide resistance. Rotate: Diamide (Chlorantraniliprole) → Macrolide (Emamectin) → Spinosyn (Spinosad). Do not repeat the same molecule more than twice per season. Remove and destroy heavily infested plant parts.
Which crops are at risk?
Tap a crop for the full pest management guide.
Bollworm — Common Questions
What is the difference between Helicoverpa and spotted bollworm?
Helicoverpa armigera (American bollworm) bores into fruits and bolls creating a characteristic round entry hole with the head visible. Spotted bollworm (Earias spp.) mainly attacks shoot tips and young bolls, causing 'dead hearts' in young plants. Both require different pheromone lures for monitoring.
What is the ETL threshold for bollworm?
The Economic Threshold Level (ETL) for Helicoverpa in cotton is 8 moths per pheromone trap per week, or 1 larva per plant at early squaring stage. For tomato, spray at the first sign of fruit damage. Do not wait until visible infestation is widespread.
What is the best spray timing for bollworm control?
Spray in the evening (after 5pm) when Helicoverpa larvae are most active and feeding on the plant surface. Avoid spraying during flowering hours to protect pollinators. Ensure full coverage of fruiting bodies where eggs are laid and larvae enter.
Still struggling with bollworm?
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