Is lack of mating competitiveness in spring linked to mating asynchrony between wild and mass-reared codling moths from an operational sterile insect programme

Mating competitiveness and pheromone trap catches of mass-reared, male codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), from the Osoyoos, British Columbia, Canada, mass-rearing facility operated by the Okanagan-Kootenay Sterile Insect Release Board, were compared to wild males using mark-release-recapture field experiments in spring, summer, and autumn at Summerland, British Columbia. In spring, significantly more wild diapause males mated with tethered, wild females than did non-irradiated (0 Gy) or irradiated (100 or 250 Gy) non-diapause, mass-reared males. A lower dose of radiation did not improve mating competitiveness, nor catches of mass-reared males released in spring. Median mating time for wild males was approximately 45 min earlier than mass-reared males with most wild males (70.5%) mating before sunset and mass-reared males mating at or shortly after sunset in spring. Superior mating competitiveness of wild males in spring was mirrored by greater recapture rates in pheromone-baited traps. In summer, mating competitiveness of mass-reared moths improved relative to wild males and there was a significant inverse relationship between radiation dose (0, 100, and 250 Gy) and competitiveness of mass-reared males. In autumn, untreated, wild males were significantly more responsive to pheromone traps than non-diapausing mass-reared males receiving 250 Gy of radiation. Mass-reared males, subjected to diapause-inducing conditions as larvae and emerged from diapause before this irradiation treatment, were recaptured significantly more often than similarly irradiated, non-diapause, mass-reared males, but not more than untreated, diapause wild males. We hypothesize that differences between wild and mass-reared males in daily timing or speed of responses to natural or synthetic pheromone sources under montane weather patterns typical of spring in British Columbia may partially explain poor activity of sterile males, and low sterile : wild overflooding ratios during spring when measured using pheromone traps by the sterile insect release programme in British Columbia.