PHARMACOKINETICS OF FENVALERATE IN LABORATORY AND FIELD STRAINS OF HELICOVERPA-ZEA (LEPIDOPTERA, NOCTUIDAE)

Pharmacokinetics of fenvalerate-C-14 were examined in the bollworm, He licoverpa erpa (Boddie), 3rd instars from a pyrethroid-susceptible str ain (BCIRL-S), a field strain (ARK) that possessed a low level of resi stance to this pyrethroid (resistance ratio 2.7-fold at LD(90)), and a composite strain (HZC) that was reared under pyrethroid selection but did not significantly differ from ARK larvae in its suceptibility to fenvalerate. We observed differences in rates of fenvalerate penetrati on and degradation among larvae from the 3 strains. Based on actual di sappearance of total radiocarbon from the insect rinses, half-times fo r fenvalerate penetration were approximate to 7, 16, and 18 h in BCIRL -S, ARK, and HZC 3rd instars, respectively. Fenvalerate was degraded f astest by HZC larvae followed by BCIRL-C and ARK larvae. The only diff erence in fenvalerate pharmacokinetics likely related to toxicity was slower pyrethroid penetration in the ARK and HZC strains as compared w ith the BCIRL-S strain.