The efficacy of some conventional insecticides in protecting cotton from bollworm injuries was assessed in laboratory bioassays, by transferring larvae on treated cotton leaf disks. Active ingredients such as endosulfan and indoxacarb exerted shock effect on H. armigera, irrespective of larval stage. On the other hand, lost of susceptibility for cypermethrin was observed in field collected populations of H. armigera. Other bollworm pests were properly controlled by cypermethrin, endosulfan and spinosad, with the exception of indoxacarb for Diparopsis watersi. Simulated rain of 24 mm two hours after insecticide application significantly reduced efficacy of cypermethrin, indoxacarb and endosulfan, but with no effect on spinosad. The same intensity of rain applied at 12 and 24 hours after insecticide application affected only the efficacy of indoxacarb. Endosulfan and spinosad showed greater persistence than indoxacarb and cypermethrin, with efficacies 50 % of on days 12, 12, 8 and 6 respectively after application. Simulated rain of 24 mm at 3 daily interval significantly reduced the persistence of all insecticides by about 66%. Insecticide properties regarding persistence and shock effect on the different species and larval stages of cotton bollworms should be used for target pest management.