Pharmacokinetics of fenvalerate in laboratory and field strains of Helicoverpa zea (Lepidoptera: Noctuidae)

Pharmacokinetics of fenvalerate-C-14 were examined in the bollworm, Helicoverpa erpa (Boddie), 3rd instars from a pyrethroid-susceptible strain (BCIRL-S), a field strain (ARK) that possessed a low level of resistance 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 penetration and degradation among larvae from the 3 strains. Based on actual disappearance of total radiocarbon from the insect rinses, half-times for fenvalerate penetration were approximate to 7, 16, and 18 h in BCIRL-S, ARK, and HZC 3rd instars, respectively. Fenvalerate was degraded fastest by HZC larvae followed by BCIRL-C and ARK larvae. The only difference in fenvalerate pharmacokinetics likely related to toxicity was slower pyrethroid penetration in the ARK and HZC strains as compared with the BCIRL-S strain.