Fenvalerate cross-resistance in a resmethrin-selected strain of the house fly (Diptera: Muscidae).

Abstract

Resmethrin-selected house flies, Musca domestica L., were cross-resistant to fenvalerate. Fenvalerate was between 30- and 100-fold less toxic to resmethrin-selected flies (R) than to susceptible flies (S). While both DEF (S,S,S-tributyl phosphorotrithionate) and piperonyl butoxide (PB) significantly synergized fenvalerate ( P < 0.05) in R flies, PB was 8-fold more effective than DEF. PB was not a good synergist in S flies. In R flies, PB did not affect the rate of fenvalerate penetration as measured by unpenetrated insecticide. GA4-282, (2,6-dichlorobenzyl-2 propynyl) ether, and PB synergized pyrethrins, resmethrin, and the carbamates Mobam™, propoxur, and mexacarbate; the propynyl ether was more effective than PB with the carbamates, whereas PB was the better synergist for pyrethrins and resmethrin was synergized equally. GA4-282 had no effect on fenvalerate toxicity, although PB was markedly synergistic.