Emission characteristics of a polyethylene pheromone dispenser for mating disruption of codling moth (Lepidoptera: Tortricidae)

Evaporative release characteristics of a polyethylene dispenser containing a mixture of (E,E)-8,10-dodecadien-1-ol (E8,E10-12:OH), dodecan-1-ol (12:OH), and tetradecan-1-ol for disruption of mating of the codling moth, Cydia pomonella (L.), were evaluated. The factors examined for each pheromone component were temperature, dispenser age, and exposure to sunlight. Increases in temperature caused an exponential increase in the release rate of each component. Evaporation rates declined over time for each component and were expressed as a function of accumulated degree-hours (DH). The combined effect of accumulated DH and instantaneous temperature (T) on release rates of dispensers placed in the orchard canopy was described by the equation ln(release rate) = a + b(1/T) + c(DH), where a, b, and c are regression coefficients specific for each component, T is temperature (degrees Kelvin), and DH is degree-hours accumulated above 0 degrees Kelvin in the orchard. Differences in evaporation rates for each component changed both the ratio of the pheromone blend inside the dispenser and that released from dispensers over time. The model did not predict evaporation rates as well for dispensers placed in full sun or total shade. In full sun, evaporation rates of E8, E10-12:OH declined significantly faster than from dispensers placed in partial sun. No significant differences were found for the evaporation rate of 12:OH or 14:OH among full or partial sun or complete shade over time. A tacky film formed on the exterior surface of dispensers exposed to sunlight. A portion of this film consisted of pheromone components in a ratio different from that found within the dispenser. Removal of this surface film from the dispenser significantly increased rates of evaporation of 12:OH and E8,E10-12:OH.