Toxicity of Seven Insecticides to Malathion-Resistant Red Flour Beetles13

Abstract

Malathion-resistant adults of Tribolium castaneum (Herbst) were tested to determine their susceptibility to pirimiphos-methyl, dichlorvos, naled, methamidophos, acephate, bufencarb, and permethrin. Cross resistance was not detected to any of the insecticides at the LD50 level, and only low levels of cross resistance were observed to acephate and naled at the LD50 level. All 7 insecticides were as toxic to the resistant strain as they were to the susceptible strain. Bufencarb, which was the least toxic, was 7× and 56× more toxic at the LD50 and LD95 levels, respectively, to the malathion-resistant strain than to the susceptible strain. Pirimiphos-methyl was the most toxic to both the susceptible and resistant strains and was more toxic than malathion.