Resistance to the insecticides lufenuron and propoxur in natural populations of Drosophila melanogaster (Diptera: Drosophilidae)

Lufenuron is a newly marketed benzoylphenyl urea chitin-synthesis inhibitor insecticide that is effective against certain insects, including Drosophila melanogaster (Meigen). Resistance to this class of insecticides is not widespread in pest insect populations and, for the resistance that has been reported, the genetic basis is not understood. In previous work, natural population strains of D. melanogaster from 2 widely 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 cross-resistance that evolved to an earlier, widely used insecticide. In the current study we examined cross-resistance of selected D. melanogaster strains to propoxur, a likely candidate carbamate insecticide that has been extensively used during the past 3 decades. However, no correlation between resistance to lufenuron and propoxur was found. Strains were selected to represent a range of dates of establishment (1936-1996) from natural populations to laboratory culture. Examination of these strains showed susceptibility to propoxur in long-established laboratory strains, but resistance in recently established strains. Susceptibility to lufenuron was also high in long-established strains and apparently slowly decreased in natural populations until approximate to 5 yr ago, when it decreased more rapidly. These results suggest that if this loss in susceptibility results from agricultural chemical usage, then these chemicals can significantly affect a non-target insect.