RESISTANCE TO THE INSECTICIDES LUFENURON AND PROPOXUR IN NATURAL-POPULATIONS OF DROSOPHILA-MELANOGASTER (DIPTERA, DROSOPHILIDAE)

Lufenuron is a newly marketed benzoylphenyl urea chitin-synthesis inhi bitor insecticide that is effective against certain insects, including Drosophila melanogaster (Meigen). Resistance to this class of insecti cides is not widespread in pest insect populations and, for the resist ance that has been reported, the genetic basis is not understood. In p revious work, natural population strains of D. melanogaster from 2 wid ely separated locations in the United States were found to be as much as 100 times more resistant to lufenuron when compared with laboratory strains. It was postulated that this resistance is the result of cros s-resistance that evolved to an earlier, widely used insecticide. In t he current study we examined cross-resistance of selected D. melanogas ter strains to propoxur, a likely candidate carbamate insecticide that has been extensively used during the past 3 decades. However, no corr elation between resistance to lufenuron and propoxur was found. Strain s were selected to represent a range of dates of establishment (1936-1 996) from natural populations to laboratory culture. Examination of th ese strains showed susceptibility to propoxur in long-established labo ratory strains, but resistance in recently established strains. Suscep tibility to lufenuron was also high in long-established strains and ap parently slowly decreased in natural populations until approximate to 5 yr ago, when it decreased more rapidly. These results suggest that i f this loss in susceptibility results from agricultural chemical usage , then these chemicals can significantly affect a non-target insect.