Toxicity of different insecticides against malathion resistant and susceptible strains of Tribolium castaneum (Herbst)

The toxicity of commonly used insecticides viz., malathion, dichlorvos, deltamethrin, cypermethrin and bifenthrin was studied against susceptible as well as malathion resistant strain of Tribolium castaneum. Malathion was more toxic than dichlorvos to susceptible strain in comparison to resistant strain but both showed lower toxicity than synthetic pyrethroids. Malathion resistant strain showed more cross-resistance to synthetic pyrethroids as compared to Dichlorvos. Deltamethrin was most toxic to susceptible as well as malathion resistant strain of T. castaneum.