How effective is chlorpyrifos-methyl against cotton bollworm (Helicoverpa armigera)? The key lies in application timing.

Cotton bollworm (Helicoverpa armigera) is a common pest on cotton, frequently active on the undersides of leaves and tender shoots. When pest populations are high, leaves are chewed and plant vigor declines. Timely intervention and precise targeting of the affected plant parts are key to controlling cotton bollworm—Chlorpyrifos-methyl 40% EC is registered for use against cotton bollworm on cotton.

Helicoverpa armigera is most susceptible and easiest to control during the early instar larval stages, when resistance is low. Once the population surges and leaf rolling occurs, insecticide application becomes both costly and difficult to manage. Before spraying, determine whether the larvae are located on the adaxial or abaxial leaf surface, and whether they are in the whorl or the ear, so that the target sites can be thoroughly and effectively covered.

Chlorpyrifos-methyl 40% EC (Emulsifiable Concentrate), Registration No. PD20100477 (subject to the actual label). Applied to cotton for controlling cotton bollworm (Helicoverpa armigera) at a dosage of 133–173.5 mL per mu, diluted with water and sprayed. Apply during the early larval stage, with supplementary applications at intervals of 7–10 days depending on pest pressure. Observe the pre-harvest interval (PHI).

Ensure thorough spray coverage of all primary infestation sites, including the undersides of leaves and tender shoots. For chlorpyrifos-methyl EC, rotate with insecticides of different modes of action to delay resistance development. Adhere to the pre-harvest interval and avoid application during bee foraging periods. Always follow the label instructions.