Studies on the Mechanism of Permethrin Resistance in Amblyseius fallacis (Acarina: Phytoseiidae) Relative to Previous Insecticide Use on Apple1

Abstract
Six strains of a predator mite, Amblyseius fallacis Garman, were studied to investigate mechanisms of permethrin resistance as influenced by previous DDT, azinphosmethyl, carbaryl, and permethrin selection. Based on synergist and LC50 studies, a mixed-field strain selected with permethrin in the laboratory had a kdr type mechanism. DDT resistance in two other field strains may be of a DDTase type. Oxidative activity was only detectable in one carbaryl-selected strain at low levels, indicating that the mixed-function oxidases were not a major resistance mechanism in these mites. Azinphosmethyl resistance was primarily due to a hydrolytic esterase-type mechanism. Permethrin resistance in A. fallacies appears to be due to kdr or esterase activity to varying extents in several resistant strains.