Pink bollworm
Cotton’s most serious pest — a pink caterpillar that bores unseen into buds and bolls, eats the seed and lint, and has overcome Bt cotton in many areas.
- Pest type
- Boring caterpillar
- Attacks
- Flower buds, flowers, bolls
- Worst in
- Boll development; late crop
- Main risk
- Hidden boll damage; Bt resistance
Overview
Pink bollworm is now the most damaging pest of cotton in India. The small moth lays eggs on squares (flower buds), flowers and young bolls; the caterpillar bores in and feeds hidden inside on the developing seed and lint, so most of the damage happens out of sight.
A classic early sign is the "rosette flower" — the caterpillar webs the petals together so the flower cannot open properly and looks like a twisted rosette. Later, bolls have tiny entry holes (often plugged), stained lint, damaged locules and pink caterpillars inside. Crucially, pink bollworm has developed resistance to Bt (Bollgard) cotton across much of India, so Bt alone can no longer be relied on — pheromone-trap monitoring, timely termination of the crop and IPM are now essential.
How to identify it
- Rosette flowers — petals webbed together so the flower cannot open and looks twisted.
- Tiny entry holes on bolls (often plugged with frass), and on opening, pink caterpillars, eaten seeds, stained lint and damaged locules.
- Double-seed / interlocked seeds inside the boll, a classic pink bollworm sign.
- Pheromone (gossyplure) traps catching the moths signal egg-laying and time control.
The damage it does
- Bored buds, flowers and bolls with the developing seed and lint eaten from inside — direct loss of the harvested product.
- Stained, weakened lint and reduced boll weight and ginning outturn, downgrading the cotton.
- Hidden damage that shows late, so a heavy infestation can be well established before it is obvious.
- Resistance to Bt cotton in many areas, so the built-in protection can no longer be relied on alone.
When to act
- Put up gossyplure pheromone traps from the squaring/flowering stage and count moths to time control on the recommended threshold.
- Open a sample of flowers and green bolls weekly to check for rosettes and caterpillars — do not wait for visible boll damage.
- Terminate the crop on time and avoid extended/ratoon cotton, which lets pink bollworm carry over and build up.
Organic & cultural control
- Use pheromone traps for monitoring and mass-trapping, and mating-disruption (PB-rope / pheromone) technology where available — a key IPM tool against pink bollworm.
- Follow a timely, defined sowing window community-wide, terminate the crop promptly after the main picking, and never carry a ratoon crop.
- Remove and destroy rosette flowers and damaged/infested bolls, and destroy cotton stalks and unopened bolls after harvest to kill overwintering larvae.
- Release Trichogramma and conserve natural enemies; avoid early broad-spectrum sprays that flare sucking pests.
Chemical control
- Spray on threshold from trap catches and boll/flower sampling, targeting eggs and young larvae before they bore into bolls — CIB&RC-registered options for pink bollworm are used and rotated by group.
- Rotate insecticide chemistries strictly and avoid repeated pyrethroids to slow further resistance.
- Do not rely on Bt cotton alone where resistance is reported; combine it with monitoring, timely termination and IPM.
- Confirm the current recommendation and dose for your area with your local KVK or the state cotton advisory.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Frequently asked questions
My cotton flowers are twisted and won’t open properly. What is it?
That is a "rosette flower", a classic early sign of pink bollworm — the caterpillar webs the petals together so the flower cannot open. Inside the crop you will also find tiny entry holes in bolls, pink caterpillars, and eaten seed and stained lint. Start monitoring with pheromone traps and act before the boll damage becomes heavy.
I grow Bt cotton — why do I still get pink bollworm?
Because pink bollworm has developed resistance to Bt (Bollgard) cotton across much of India, so the built-in protection no longer reliably kills it. Bt alone can no longer be trusted for this pest. You now need pheromone-trap monitoring, timely crop termination, destruction of stalks and bolls, mating disruption where available, and threshold-based rotated sprays.
Why is timely crop termination so important?
Because a prolonged or ratoon cotton crop gives pink bollworm continuous bolls to breed in and lets it carry over to the next season. Terminating the crop promptly after the main picking, destroying stalks and unopened bolls, and following a community-wide sowing window break the pest’s cycle — one of the most effective steps against it.
Symptoms and control measures follow ICAR, KVK and state agricultural-university package-of-practices; any named chemical is a registered use. Always read the product label and confirm the dose for your crop and zone. editorial policy.