American Bollworm Control

Symptoms

Watch for round bore holes on squares, flowers and bolls, with larvae often hanging out with the head inside the boll and the rest of the body outside. Damaged squares and young bolls shed, and you see large greenish to brown caterpillars with lengthwise stripes feeding on fruiting parts.

Damage

American bollworm (Helicoverpa armigera) is a polyphagous pest that bores into squares and bolls and destroys the seed and lint. A single larva can damage many bolls as it moves from one to another. Severe attack causes heavy shedding of fruiting bodies and can lead to 20 to 50 percent yield loss.

Organic & cultural control

Install pheromone traps with Helilure at 5 traps per hectare for monitoring. Set up bird perches at 20 to 25 per hectare. Release Trichogramma chilonis egg parasitoids and spray HaNPV (Helicoverpa nuclear polyhedrosis virus) in the evening. Use neem seed kernel extract 5 percent and conserve natural enemies like Chrysoperla and spiders. Hand pick and destroy grown larvae.

Chemical control

When larvae cross the economic threshold, recommended actives such as emamectin benzoate, chlorantraniliprole, flubendiamide, spinosad, indoxacarb or quinalphos can be used in rotation to avoid resistance. Avoid repeated use of the same group. Always read and follow the product label, observe the pre-harvest interval, and consult your KVK or a qualified agronomist before spraying.

Always follow the product label, the recommended pre-harvest interval, and your local KVK or agronomist. Pesticide approvals change, so verify before use.

Prevention

Sow on time with recommended varieties and avoid excess nitrogen that promotes lush growth. Grow trap crops such as marigold or pigeonpea on field borders to attract egg laying. Keep fields weed free, monitor with pheromone traps, and intercrop to support natural enemies. Deep summer ploughing exposes resting pupae to predators and sun.