METABOLISM OF ESFENVALERATE BY PYRETHROID-SUSCEPTIBLE AND PYRETHROID-RESISTANT AUSTRALIAN HELICOVERPA-ARMIGERA (LEPIDOPTERA, NOCTUIDAE)

Esfenvalerate metabolism in pyrethroid-resistant and -susceptible Aust ralian Helicoverpa armigera larvae was studied using in vivo and in vi tro methods. Data from both methods showed very little evidence of esf envalerate metabolism in the susceptible strain. In a resistant strain , esfenvalerate metabolism was only slightly enhanced, as evidenced by traces of several labelled and nonlabelled metabolites in the excreta and internal fractions. Piperonyl butoxide did not inhibit this metab olism; however, there was evidence that it may facilitate esfenvalerat e penetration in the resistant insects, presumably, increasing the ava ilable internal dose. Reduced penetration of esfenvalerate appeared to be an important resistance mechanism in the resistant strain. (C) 199 5 Academic Press, Inc.