An attempt to increase efficacy of moth mating disruption by co-releasing pheromones with kairomones and to understand possible underlying mechanisms of this technique.

Pheromone-based mating disruption is used worldwide for management of the internal fruit feeding codling moth, Cydia pomonella (L.). There has been recent interest in the potential of improving mating disruption of C. pomonella, and potentially other insect species in general, by broadcasting combinations of pheromone and attractive host-plant kairomones. Given that such kairomones are attractive by themselves (often to both sexes), and also enhance male moth response to their pheromone, it is possible that the effects of competitive attraction and potentially other mechanisms of disruption might be increased. Herein, we tested the hypothesis that mating disruption of C. pomonella could be enhanced by co-deploying pheromone with either of two kairomones: (2E, 4Z)-2, 4-decadienoate (pear ester), or (E)-β-farnesene, as compared with various pheromone blend components alone. When deployed individually, each kairomone caused a low level of synthetic lure trap disruption and (E)-β-farnesene also caused disruption of mating as measured by tethering virgin females. However, combined release of either pear ester or (E)-β-farnesene with pheromone within the same dispenser or as a co-deployed dispenser treatment, respectively, did not increase the level of mating disruption as compared with deploying pheromone alone. Disruption efficacy did not decline when reducing the amount of (E,E)-8,10-dodecadien-1-ol (codlemone) in dispensers by fourfold, when combined with pear ester. C. pomonella readily were observed briefly approaching all dispenser types (with and without pheromone) in the field. Exposure of male C. pomonella to pear ester alone in a manner mimicking observed field exposures did not reduce the number of males able to contact a female-mimic pheromone lure in flight tunnel assays. Also, reduction of male moth behavioral response to pheromone was similar after exposure to codlemone alone, and codlemone and pear ester after exposures that mimicked those observed in the field and none of the main treatments tested (pheromone versus pheromone and either kairomone) affected male moth antennal response seconds after exposure as measured by electroantenogram assays. Collectively, our data indicate that disruption of C. pomonella was not improved by co-releasing pheromone with either kairomone tested from point source devices as compared with pheromone alone at the relatively high loading dosages and associated release rates tested.