Antennal and behavioral responses of virgin and mated oriental fruit moth (Lepidoptera: Tortricidae) females to their sex pheromone

Abstract

Electroantennogram (EAG) and behavioral responses of female oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), were studied using the synthetic major component, (Z)-8-dodecenyl acetate, and partial three-component blend, (Z)-8-dodecenyl-acetate: (E)-8-dodecenyl-acetate: (Z)-8-dodecenol (in a 93:6:1 ratio), of the sex pheromone. EAGs elicited by both the single and three-component pheromone were significantly greater compared with hexane solvent controls. In 1-liter plastic chambers with constant throughput of air (50 ml/min) over rubber septa loaded with 0.01 or 0.1 mg of the three-component pheromone blend, onset of female calling was advanced by ≈2 h compared with solvent controls. However, the total number of females calling at peak time and the time of calling termination did not differ between pheromone-exposed and control moths. Oviposition rates of pheromone-exposed and clean air-exposed mated female moths did not differ in similar 1-liter flow-through chambers lined with wax paper over 24-h intervals. In a separate experiment, male and female oriental fruit moth, caged in perforated 1-liter containers allowing air ventilation, were placed for 1-wk intervals in replicated glasshouses that were either treated with Isomate dispensers hung 0.5 m from chambers or left untreated. Oviposition rates between Isomate dispenser-exposed and control moths were similar. Female sensitivity to sex pheromone, termed "autodetection," has been observed previously and is thought to function either as a mechanism to 1) advance female calling periodicity under high population densities to increase the probability of attracting males, 2) induce dispersal under high population densities to reduce competition for males or food resources, or 3) aggregate females to increase local probability of mating success. Autodetection also may affect the efficacy of mating disruption for oriental fruit moth depending on whether pheromone exposure affects the diel periodicity of male sexual response. © 2006 Entomological Society of America.