Cotton Bollworm

Larvae vary considerably in colour, from green or yellow-brown to pink, often with faint dark stripes along the body, and reach around four centimetres at maturity. A round entry hole with frass on the surface of a boll or fruit, and a larva feeding within, are the clearest field signs.

Adult moths are stout-bodied and pale brown with darker markings, and are night-flying, so scouting typically relies on eggs, larvae, and damage signs rather than adult sightings.

Females lay eggs singly on leaves, flower buds, and fruiting structures. Young larvae feed briefly on foliage and flowers before moving into bolls or fruit, where later instars cause the most damage. Multiple overlapping generations typically occur within a season in warm climates.

The species can migrate over considerable distances as an adult, and can also enter a resting (diapause) stage in some regions to survive unfavourable seasons.

Larvae feeding on flower buds cause them to drop, while boring into bolls destroys developing lint and seed and creates entry points for secondary rots. Larvae typically move between several bolls or fruit during development, damaging more than they consume.

Host crops include cotton, tomato, maize, and sorghum, among many others, reflecting the species’ unusually broad host range.

Pheromone traps for adult moths, combined with regular field scouting for eggs and small larvae on squares, flowers, and young bolls, are the basis of monitoring programmes and help time any intervention before larvae bore into fruiting structures.

Because Helicoverpa armigera has repeatedly developed resistance to insecticides, management emphasises diversified, integrated tactics rather than reliance on chemical control alone.

• Scout regularly and target the vulnerable egg and young-larval stages
• Conserve parasitoid wasps and flies, predatory bugs, and other natural enemies
• Use resistant or tolerant varieties and trap crops where available
• Rotate modes of action and follow local resistance-management guidance where insecticides are used