Wilson_1996_Pestic.Biochem.Physiol_54_85

Seven possible nonoxidative mechanisms which might contribute to resistance to organophosphate insecticides have been examined in larvae and adults from field isolates of the sheep blow fly,Lucilia cuprina,selected for resistance to diazinon. The basal resistance mechanism appears to be an altered esterase (the E3 esterase). In addition, in adults, there is a strong correlation between resistance to diazinon and the glutathioneS-transferase activity with 3,4-dichloronitrobenzene as substrate. This correlation is marginal in the larvae of this species. There was also a marginal negative correlation between the resistance to diazinon and the rate of inactivation of acetylcholine esterase by tetrachlorvinphos. No significant degree of correlation was found between resistance to diazinon and total esterase, with either alpha- or beta-naphthyl actetate as substrate, total acetylcholine esterase activity, or glutathioneS-transferase using 1-chloro-2,4-dinitrobenzene as substrate. Significant correlations were found between resistance to diazinon and that to other organophosphate insecticides including chlorpyrifos, propetamphos, and dichlofenthion. In light of these correlations, it is concluded that the same basic mechanisms of resistance are operating with respect to all of these insecticides. Since the field isolates were sampled over a wide geographical range and over several years, it appears that the mechanisms of resistance are stable and widely distributed.