Submitted to: The Canadian Entomologist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/12/2005
Publication Date: 11/1/2005
Citation: Knight, A.L., Light, D.M. 2005. Developing action thresholds for codling moth (Lepidoptera: Tortricidae) with pear ester and codlemone-baited traps in apple orchards treated with sex pheromone mating disruption. Can. Entomol. 137(6):739-747. Interpretive Summary: Most apple growers place sex pheromone lure-baited traps in their orchards to monitor codling moth in order to avoid fruit injury. Moth catches are useful to characterize the pest density and to recommend the need for supplemental control. The pear ester is a chemical isolated from pear that is attractive to both sexes of codling moth. Research at the Yakima Agricultural Research Laboratory is focused on developing this chemical as a new lure for codling moth that would be more effective than the sex pheromone lure in orchards treated with sex pheromone for mating disruption. Studies were conducted in a large number of orchards over three years and the reliability of using cumulative moth catches in both pear ester and sex pheromone-baited traps at different times in the season to predict the occurrence of fruit injury by codling moth was assessed. Thresholds developed with the pear ester lure were more effective than sex pheromone lures in preventing instances where traps failed to warn growers of moth population densities sufficient to cause fruit injury.
Technical Abstract: Traps baited with either ethyl (E, Z)-2, 4-decadienoate (pear ester) or (E, E)-8,10-dodecadienol (codlemone) were used to develop action thresholds for codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae) in apple, Malus domestica Borkhausen (Rosaceae), orchards treated with sex pheromones. Studies were conducted in 102 orchards treated with 500 – 1,000 Isomate-C Plus dispensers per ha during 2000 – 2002. Pairs of traps were placed within two 1.0 ha plots within each orchard and nearby fruit injury was assessed at mid-season and prior to harvest. The numbers of female and total numbers of moths caught in pear ester-baited traps and males caught in codlemone-baited traps were used to develop action thresholds. Thresholds were chosen based on a criterion where the cumulative moth catches per trap exceeded the threshold in < 5% of the traps placed in unsprayed plots with no fruit injury (false positive catches). Specific thresholds were established for the first spray timing (139 degree days after the start of moth catch in sex pheromone-baited traps) and for the 1st and 2nd moth flights. The occurrence of false negative cumulative moth catches at 1st spray timing in plots with subsequent mid-season fruit injury was determined with these established action thresholds and when the thresholds were reduced incrementally to > 1 moth per trap. False negative moth catches were less common in plots with high levels of fruit injury (> 0.3%) than with low levels of fruit injury and more common with codlemone than pear ester-baited traps. An action threshold of > 1 moth in a pear ester-baited trap at 1st spray timing eliminated the occurrence of false negative moth catches.