Emission characteristics of 3 sex pheromone components, (E,E)–8, 10–dodecadien– 1–01[codlemone], 1–dodecanol, and I–tetradecanol, of codling moth,Cydia pomonella(L.), were determined from a polyethylene tube dispenser. A model predicting emission rate of codlemone as a function of accumulated degree hours and temperature was developed. The effectiveness of different blends and estimated emission rates of codlemone at dusk in disrupting sexual communication of codling moth were evaluated in field tests in apple (Malus X domestica[Borkham]) during 1991–1992. In all field tests, virgin female–baited traps and releases of marked male moths were used. Traps were placed at 3 heights in the canopy in 9 orchards treated with 1,000 polyethylene tube dispensers per hectare and a single untreated orchard. Trap height significantly affected moth catch in both the pheromone–treated and untreated orchards. The difference in moth catches between pheromone–treated and the untreated orchard with respect to the estimated codlemone emission rate at dusk was substantial for each height, and tile slopes did not differ among heights. A significant negative regression was found for moth catch and the estimated codlemone emission rate from fibre dispensers aged in the field 0–120 d in small plots (0.1 hal. No difference in moth catch was found for plots treated with Celcon hollow fiber dispensers emitting codlemone versus a 3–component blend. Emission rate was a significant factor affecting moth catch. Problems associated with using these data to establish a minimum effective pheromone emission rate for disruption of codling moth are discussed.