Effect of monitoring trap and mating disruption dispenser application heights on captures of male Grapholita molesta (Busck; Lepidoptera: Tortricidae) in pheromone and virgin female-baited traps

Studies were conducted in 0.07- to 0.18-ha peach and apple plots to determine the effects of pheromone trap and hand-applied emulsified wax pheromone dispenser application heights on captures of Grapholita motesta in traps baited with pheromone lures or virgin females. Traps and pheromone dispensers were placed either low (1.2-1.8 m) or high (2.7- 4 m) within tree canopies. In the majority of cases, equivalent numbers of mate G. raolesta were caught in traps placed at the low and high positions in both pheromone-treated and untreated plots. Furthermore, pheromone dispensers placed at the low and high positions equally disrupted orientation of male G. molesta to pheromone traps placed at either height and to virgin female traps placed at 1.2-1.8 m within canopies season-long at most sites. Our results indicate that for trees <= 3.5 m tall, dispensers with release rates >= 18 mg/ha/h placed at 1.5-2.0 m (heights easily reached from the ground) should effectively disrupt mating of G. molesta throughout tree canopies. In trees between 3.5 and 4.5 m tall, the dispensers should be moved to approximate to 1.5 m from the top of the canopy. For trees taller than 4.5 m, we recommend hanging dispensers both in the top and bottom thirds of tree canopies. Most commercial Michigan peach and apple trees are < 3.5 m tall. Eliminating the need to apply dispensers high in the canopy in most orchards will enable growers to reduce application costs, thereby facilitating increased adoption of mating disruption for G. molesta control by growers.