Efficacy of some pyrethroids against a strain of the rabbit ear mite (Psoroptes cuniculi ): an unusual cross-resistance pattern

Abstract

An in vitro immersion bioassay was used to compare the efficacy of selected pyrethroids against a deltamethrin-resistant strain of rabbit ear mite (Psoroptes cuniculi). A lack of cross-resistance between bromo (deltamethrin) and chloro analogues (cypermethrin) of α -cyano-3-phenoxybenzyl - dihalovinyl-dimethylcyclopropane carboxylate was detected. Whereas deltamethrin proved to be inactive (48-h mortality 21.9% at 1000 mg/kg), each cypermethrin isomer mixture tested, including alpha-cypermethrin [1R(cis) α S + 1S (cis) α R] and theta-cypermethrin [1R(trans) α S + 1 S (trans) α R] and their mixture at a ratio of 4/6, beta-cypermethrin, showed high efficiency (48-h  mortality ≥ 95% at 1000 mg/kg).