Conditions that Favor Mating Disruption of Epiphyas postvittana (Lepidoptera: Tortricidae)

Abstract

Mating disruption of Epiphyas postvittana (Walker) using Shin-Etsu dispensers that contained ( E )-11-tetradecenyl acetate and ( E , E )-9,11-tetradecadienyl acetate was investigated using pheromone traps, tethered virgin female moths, and assessment of larval damage in apples at harvest in small orchard blocks (<0.5 ha). Pheromone trap catches were completely suppressed for 9 mo by a single application of synthetic pheromone. Catches did not return to control levels for 12 mo. Mating disruption, investigated for 94 wk, was completely achieved in 100% of weeks when average weekly release rates were ≥12 mg/ha per h, in 84% of weeks with 8–12 mg/ha per h, and in 68% of weeks with <5 mg/ha per h. The majority of failures to disrupt mating occurred in the following spring. Along with low pheromone release rate, coincident high activity of males outside the orchards (1–2.5 males per trap per day) appear likely to be major factors in 90% of failures to disrupt mating completely within the orchards. A change from pheromone blend close to the natural blend to one with significantly more isomeric impurity (a change from ≈3 to 30%, (Z)-11-tetradecenyl actetate) did not adversely affect efficacy, measured by prevention of trap catch or mating of tethered females. Trap catch 50 m outside treated blocks was correlated with frequency of mating by tethered females 5 m away, but the parameters were not related to fruit damage by larvae at harvest on the nearest orchard border.