Gunning_1996_Pestic.Biochem.Physiol_54_12

Larvae of pyrethroid-resistant Australian Helicoverpa armigera have enhanced esterase activity which is due to increased production of the enzymes. The most resistant individuals have approximately a 50-fold increase in esterase activity compared to susceptible populations. Resistant H. armigera have additional esterase bands which are not detected in susceptible individuals. Increased esterase hydrolysis of 1-naphthyl acetate was correlated to the esfenvalerate resistance factor. Esterase bound readily to esfenvalerate. Homogenates of resistant insects hydrolyzed esfenvalerate and it is also likely that there was significant detoxification by sequestration. The prospect of biochemical assays for pyrethroid resistance and the possible genetic basis of the esterase resistance mechanism are discussed.