Submitted to: The Canadian Entomologist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/5/2005
Publication Date: 11/1/2005
Citation: Knight, A.L., Light, D.M. 2005. Timing of egg hatch by early-season codling moth (Lepidoptera: Tortricidae) predicted by moth catch in pear ester and codlemone-baited traps. Can. Entomol. 137(6):728-738. Interpretive Summary: Growers predict the start of egg hatch of codling moth with the onset of catching male moths in sex pheromone-baited traps. Insecticide applications are timed with this approach to improve the management of this destructive pest. The limitations of this approach are that sex pheromone-baited traps catch only males and predictions of egg hatch are subject to errors due to differences between the sexes in emergence timing and variability among orchards and between years in the onset of egg laying due to the influence of cool temperatures on female moth’s sexual behaviors. Recently, a chemical derived from pear fruit, pear ester, has been shown by ARS researchers to be attractive to both male and female codling moths. Monitoring female moths directly with pear ester may allow growers to more accurately time female emergence in the season and the occurrence of egg laying by females and subsequent egg hatch. Studies were completed from 2000-2002 to compare the use of pear ester versus sex pheromone-baited traps. Our results suggest that timing egg hatch from the start of sustained catch of female codling moths in pear ester-baited traps may be an improvement over the current use of sex pheromone-baited traps. In addition, we found that the accuracy of this prediction can be further improved by selecting the exact start of female moth’s sexual activity by considering the daily maximum and dusk temperatures that occur between trap checks.
Technical Abstract: Timing of moth catch in traps to predict the start of egg hatch by first generation codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae) in apple, Malus domestica Borkhausen (Rosaceae) was evaluated with ethyl (2E, 4Z)-2,4-decadieonate (pear ester) and (E, E)-8,10- dodecadien-1-ol (codlemone) lures. Paired traps baited with either lure were placed in seven orchards and checked daily during the spring flight in 2000 and 2001. Rearing field-collected eggs and sampling fruit for injury were used to estimate the start of egg hatch. Moth catch in codlemone and pear ester-baited traps occurred approximately 144 and 105 degree days prior to the start of egg hatch, respectively. The effectiveness of using moth catch as a biological reference point (Biofix) to predict the start of egg hatch when traps were checked every 3-4 d was evaluated in 11 orchards from 2000-2002. The calendar date of first moth catch and the start of sustained moth catch (> 1 moth/trap in 2 consecutive trap checks) with either lure varied widely among orchards and years. Yet, no significant differences occurred among years in the cumulative degree day totals from any Biofix to egg hatch. Significant differences in cumulative degree days from first (Biofix 1) and first sustained (Biofix 2) moth catch until egg hatch were found among male catch in codlemone-baited traps and total and female moth catch in pear ester-baited traps. Incorporating daily temperature thresholds for maximum (> 22.2 oC) or dusk (> 15.6 oC) temperatures to adjust the Biofix (1a or 2a) significantly changed the degree days accumulated until the start of egg hatch with only the sustained catch of female moths with a pear ester lure (Biofix 2a). The use of Biofix 2a for first sustained catch of female codling moth in a pear ester-baited trap had the highest degree of accuracy and precision in predicting the start of egg hatch among the various Biofix types evaluated in our study.