Occurrence and Duration of Long-Lasting Peripheral Adaptation Among Males of Three Species of Economically Important Tortricid Moths

Abstract

Electroantennograms (EAGs) of Cydia pomonella (L.), Pandemis pyrusana Kearfott, and Grapholita molesta (Busck) documented the presence and duration of long-lasting peripheral adaptation after pheromone preexposure. Moths of each species were preexposed fo r1ht ovarying dosages (100 ngÐ100 mg) of the major components of their respective pheromone blends in 1-liter Teson containers with constant throughput of air. EAGs were performed on all insects 1 min after preexposure and at several subsequent intervals up to 120 min after exposure. Long-lasting peripheral adaptation was recorded by EAG after pheromone preexposure over a range of pheromone dosages in both C. pomonella (100 gÐ10 mg) and P. pyrusana (100 ngÐ100 mg). This reduction in EAG responsiveness lasted 60 and 10 min, respectively, for these two species. For G. molesta, a reduction in EAG responsiveness occurred only afte r1ho fexposure to the highest dosage of pheromone tested (100 mg). Recovery from adaptation was also rapid in this species: EAGs were signiÞcantly reduced to all applied stimulus dosages only at 1-min postexposure. There was substantial variation in the prevalence and duration of decreased EAG responsiveness across the species investigated. However, where long-lasting adaptation was described, the phenomenon lasted 60 min. In addition, long- lasting adaptation was induced after prolonged exposures at estimated airborne concentrations of pheromone in the range of nanograms per milliliter, which are much higher than the pheromone concentrations in Þeld plots treated with synthetic pheromone dispensers. Long-lasting peripheral adaptation after pheromone preexposure does not seem to be an important contributor to mating disruption.