NERVE INSENSITIVITY TO CIS-CYPERMETHRIN IS EXPRESSED IN ADULT HELIOTHIS-VIRESCENS

Adult and third-instar larval Heliothis virescens were examined for ne rve insensitivity to cis-cypermethrin using a rapid and robust neuroph ysiological method. Three laboratory strains, BRC susceptible, PEG-87 resistant and MS2 metabolic resistant, were compared with a series of pyrethroid-resistant strains collected from a held site in Louisiana, USA, during the 1992 cotton season. Nerve insensitivity was present in a proportion of the individuals in both the PEG-87 and the held strai ns, at both life stages, minimal in the MS2 strain and absent in the B RC strain. Frequencies of nerve-sensitive and nerve-insensitive indivi duals in each strain were not significantly different at the two life stages examined.