| Abstract: | The toxicity, metabolism, and absorption of several selected insecticides were compared between methyl parathion-susceptible (S) and -resistant (R) strains of the tobacco budworm (Heliothis virescens (F.)) to assess the influence of detoxification and absorption in the resistance exhibited by the R larvae. In addition, the relationships of certain chemical structures of dialkyloxy arylphosphate compounds to toxicity, metabolism, and absorption were evaluated. Toxicity tests made with 3rd-stage larvae indicated that the R larvae were resistant (as evidenced by a 5-fold or greater increase in the LD [subscript 50] value of an insecticide as compared with that from S larvae) to methyl parathion, methyl paraoxon, paraoxon, parathion, and fospirate, but not to chlorpyrifos, chlorpyrifosmethyl, or Dowco [superscript R] 180. Those compounds containing dimethoxy groups were more toxic than their corresponding diethoxy homologues to larvae of both strains. |
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