Investigation of the mechanisms underlying pheromone-based mating disruption

Laboratory and field investigations were conducted with four species of tortricid moth pests of apple to gain better understanding of the mechanisms mediating pheromone-based mating disruption. Electroantennogram studies revealed differences among the leafroller species, Argyrotaenia velutinana and Choristonerura rosaceana, in the onset and duration of an antennal adaptation termed long-lasting adaptation (LLA). Although this difference exists between these species, it is unlikely an important contributor to mating disruption given that the exposure concentration of pheromone required to induce LLA is well above that which can be achieved in the field. Direct observations of moth behavior in the field revealed that tortricids closely approach polyethylene-tube pheromone dispensers in untreated and pheromone-treated orchards. These dispensers are the dominant method of broadcasting pheromone for mating disruption in the U.S.A. Field-observed approaches were brief (less than 60 s) and close (within 100 cm of dispensers). Laboratory flight-tunnel studies revealed that exposures similar to those observed in the field affect subsequent behaviors of the three species investigated. However, a large proportion of each species retained capability to initiate anemotaxis and plume follow after pre-exposure. These results suggest that false-plume-following and competitive attraction between synthetic sources and authentic females are the dominant mechanism mediating mating disruption of the species investigated.