RESIDUAL ACTIVITY OF OVIPOSITION-DETERRING PHEROMONE IN RHAGOLETIS-POMONELLA (DIPTERA, TEPHRITIDAE) AND FEMALE RESPONSE TO INFESTED FRUIT

Under dry conditions, oviposition-deterring pheromone (ODP) of the apple maggot fly (Rhagoletis pomonella Walsh) on host fruit proved deterrent to ovipositing females for at least three weeks, with a half-life of ca. 11 days. There was no difference in decline of residual activity under lab vs. field conditions or between fly-deposited ODP vs. an application of a water extract of ODP. A decline in pheromone activity resulted from exposure to both natural and simulated rainfall. For natural rainfall, greatest losses (50-61%) in activity resulted from high-intensity rains, with substantially less activity lost (13-35%) following light or moderate intensity rains. R. pomonella females discriminated against fruit without ODP but with conspecific larvae. Discrimination against infested fruit was manifested within fewer days following infestation of small fruit (9 mm diam.) as compared to larger fruit (15 mm diam.).