Host plant effects on resistance to bifenthrin in silverleaf whitefly (Homoptera: Aleyrodidae)

Effects of host plants on resistance to bifenthrin in the silverleaf whitefly, Bemisia argentifolii BellowsPerring, were determined by LC50 bioassay. In addition, inheritance of resistance to bifenthrin was investigated beginning with a single source of a bifenthrin-susceptible population. Overall, the resistance ratio between the bifenthrin-susceptible population and the selected bifenthrin-resistant population from the same source population was 915-fold after 1 yr in the greenhouse. Responses to bifenthrin among the susceptible and the resistant populations were changed when whiteflies were reared on three different host plants, i.e., cotton, cabbage, and squash. In the resistant populations, the LC50 value of whitefly fed on squash was increased as much as 7.5-fold, while the LC50 value of whitefly fed on cabbage was similar to cotton that served as the control plant. The host plant on which whiteflies feed appears to be an important factor in selection for resistance to bifenthrin, but these effects are crop specific. Based on an analysis using LC50 values of the reciprocal F1 cross on cotton, resistance of whitefly from a single-source whitefly population was inherited as an incompletely dominant factor. A model used to estimate loci numbers showed that resistance of whitefly to bifenthrin is probably controlled primarily by a few or a single locus. In addition, the difference in the ratio of LC50 values between males from unmated mother and males from mated mother was approximately fivefold, suggesting that insecticide resistance in whitefly males is in some way affected by mating.