MULTIPLE MECHANISMS OF PYRETHROID RESISTANCE IN THE GERMAN-COCKROACH,BLATTELLA-GERMANICA (L)

Pyrethroid-resistant German cockroaches known as the Village Green str ain were compared to a susceptible (Orlando Normal) strain in respect to possible mechanisms of insecticide resistance. Male adults of the r esistant strain weighed 15% more than susceptible roaches of the same cumulative age from adult eclosion. Based on the topical application o f different concentrations of permethrin, the KD50 for resistant roach es was 20-times greater than that for susceptible insects. Reduced pen etration of [C-14]permethrin was observed in resistant insects during 24 hr after treatment along with increased in vivo metabolism as compa red with susceptible controls. The cytochrome P450 content and monooxy genase activity when measured with methoxyresorufin and benzo[a]pyrene was elevated in resistant roaches by as much as 6.9-fold but no diffe rence was found with benzphetamine. The glutathione transferase activi ty was also increased (1.6-fold with chlorodinitrobenzene) and elevate d esterase activity was detected with the substrates, 1-naphthyl aceta te (1.7-fold) and p-nitrophenyl acetate (2.1-fold). Using isoelectric focusing, a novel E(2) esterase was identified in resistant cockroache s not found in the susceptible population. E(2) may be partly responsi ble for the increased esterase activity observed in resistant roaches. Increased esterase activity toward p-nitrophenyl acetate was used to develop a kinetic, diagnostic assay that could rapidly discriminate re sistant from susceptible individuals. (C) 1994 Academic Press, Inc.