Abstract
A toxicokinetic model was proposed to describe the in vivo dynamics of 14C-fenvalerate applied topically to a susceptible (S) and a pyrethroid resistant (R) strains of the German cockroach. Values of various kinetic parameters, such as cuticular penetration (k1), rub-off (k2), degradation (k3), binding (k4) and excretion (k5), were estimated by computer simulation. The result showed that the penetration and rub-off rates were slower in the R strain than in the S strain. No significant difference was found in degradation, binding and excretion rates between the strains. The R strain also showed behavioral resistance to the “flushing out” effect of fenvalerate. Coupled with the results in the previous paper, it is concluded that the control failure of the R strain by pyrethroids was brought about by a combination of three factors, behavioral avoidance, decrease in cuticular penetration and insensitivity at the site of action.
