Resistance to cyfluthrin and tetrachlorvinphos in the lesser mealworm, Alphitobius diaperinus, collected from the eastern United States.

The lesser mealworm, Alphitobius diaperinus (Panzer), is an important pest in poultry facilities. The toxicity of cyfluthrin and tetrachlorvinphos to five strains of the lesser mealworm was compared with the toxicity to a susceptible laboratory strain. Bioassays were carried out with both larvae and adults. For the susceptible strain, cyfluthrin and tetrachlorvinphos had similar toxicity to adults, but cyfluthrin was 5 times more toxic to larvae when compared with tetrachlorvinphos. High levels of resistance to tetrachlorvinphos in two beetle strains were detected in both larvae and adults, although these strains were heterogeneous and still contained susceptible individuals. Resistance to cyfluthrin ranged from 1.7- to 9.5-fold for adults and from 0.5- to 29-fold for larvae at the LC(95). Overall, the patterns of resistance did not mirror the insecticide use patterns reported at these facilities. The implications of these results to management of the lesser mealworms are discussed.