Sex-Linked Altered Acetylcholinesterase Resistance to Carbamate Insecticides in Adults of the Oriental Fruit Moth, Grapholita molesta (Lepidoptera: Tortricidae),

Insecticide resistance continues to be a major problem in the production of many important horticultural and field crops. The inheritance of resistance to a carbamate insecticide was measured in adults of a resistant population of the Oriental fruit moth (OFM), Grapholita molesta (Busck), a destructive pest of peach in northeastern North America. The inheritance of variations in inhibition of acetylcholinesterase in susceptible and resistant OFM adults was determined and quantitative measurements were made of total acetylcholinesterase and nonspecific esterase activity. Resistance and acetylcholinesterase inhibition were linked to the sex chromosome and were shown to be highly correlated (r2 > 0.91), suggesting that the mutant acetylcholinesterase was the basis for most of the observed resistance in adults. Levels of nonspecific esterase activity were 2.0- to 4.8-fold higher in resistant than in susceptible OFM and twice as high in males as in females, but there was no evidence that this resistance factor was sex linked. Results of bioassays of susceptible, resistant, and F1 hybrid OFM indicated that resistance appeared to be incompletely recessive in all F1 males and in females of the (R × S) F1 progenies. In contrast, resistance appeared to be intermediate in daughters of resistant males mated with susceptible females (S × R). Because of the lack of effective alternative control strategies, the identification of actual or potential resistance mechanisms and its genetic basis in actual pests are needed to maximize and predict the likelihood of success in resistance management programs.