Topical pheromone trap assay for monitoring insecticide resistance of Phyllonorycter elmaella (Lepidoptera: Gracillariidae)

A topical pheromone trap assay was an effective method for assessing the resistance status in male Phyllonorycter elmaella (Doganlar and Mutuura) moths to the organophosphate azinphosmethyl and the carbamate oxamyl. Moths captured in pheromone-baited sticky traps were treated topically with a 0.2-microliter droplet of an insecticide solution, which was dispensed with a microsyringe to each insect. Several factors affected the mortality response of adults including trap adhesive, environmental conditions before and during the bioassay, prior field exposure to insecticide, and time of collection. The trap adhesives, Tanglefoot and Tangletrap, were inherently less toxic to captured moths than Stikem Special. High temperature and low humidity in the field before collection or later during the bioassay increased mortality. Sublethal exposure to azinphosmethyl or oxamyl in the field also increased the mortality response of moths in the bioassays. Control mortality increased toward the end of each flight period and with each generation. Leafminers from sprayed orchards were highly resistant to azinphosmethyl but are still susceptible to oxamyl. We detected no evidence for cross-resistance. Male and female moths were equally susceptible to oxamyl. In conclusion, this pheromone trap assay can provide rapid information on the susceptibility of P. elmaella populations to adulticides and help to select effective control options