Inheritance, Stability, and Reversion of Insecticide Resistance in Tobacco Budworm (Lepidoptera: Noctuidae) Field Populations

Abstract

Responses of an insecticide-resistant strain of tobacco budworm, Heliothis Virescens (F.), were examined in the laboratory by using three different insecticide bioassays during continuous culture without insecticide selection pressure. Resistance to the pyrethroid cyperrnethrin and the carbamate thiodicarb did not revert to susceptiblity until 12 generations in culture. Previous studies indicated that reversion tends to occur much more rapidly in this species. The temporal sequence of resistance in field populations of H. virescens collected in 1990 and 1991 was determined by using a spray-chamber bioassay. Resistance to several classes of insecticides varied and was often high before and during the cotton growing season. Inheritance of resistance in insecticides in H. virescens was examined with two different bioassays. Results of bioassays with third instars and adults were similar. Resistance in reciprocal crosses was intermediate to that of the parent susceptible and resistant strains. Codominant mechanisms of resistance to the pyrethroid and carbamate insecticides are suggested from the data.