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Research in BC: The Cherry Fruitworm

Research in BC: The Cherry Fruitworm

by: Emily Carmichael and Kristine Ferris, E.S. Cropconsult Ltd.

Evaluation of commercial pheromone lures for attraction of cherry fruitworm (Grapholita packardi) in the Fraser Valley

The cherry fruitworm (CFW), known scientifically as Grapholita packardi, is an occasional pest of cherries in the interior of British Columbia. It has recently become a cause for concern as it poses a threat to our Fraser Valley blueberries. In the Midwest and northeastern United States, fruitworms are the major Lepidopteron pest that directly targets blueberry fruit. Cherry fruitworm infestations have occurred on one farm in Abbotsford since 2010, causing significant damage to fruit in some years.

Cherry fruitworm has one generation per year in blueberries. In Michigan, adult moths emerge in the spring during bloom and early fruit set. Egg laying typically occurs in early June and in the two weeks following 100% petal fall. Single eggs are laid on the calyx end of the fruit and hatch 3-5 days afterwards. The larvae feed within green berries, creating large amounts of frass and webbing, rendering the berries unmarketable.

Once the larvae enter the fruit to feed, they are protected from sprays.  This means that insecticide applications must target either the eggs or newly hatched larvae. Knowing the timing of egg hatch is critical in order to successfully time an insecticide application. Pheromone trapping for CFW enables monitoring of the male moth’s flight, which can then be used to predict timing of egg laying and hatch.

During bloom in the Midwest and Northeastern U.S., moth flight is monitored with commercial cherry fruitworm pheromone lures. In 2011, area-wide surveillance for CFW was carried out on 28 farms in the Fraser Valley with sticky wingtraps baited with commercial cherry fruitworm lures. Trap catches were low and sporadic, even in the Abbotsford field where extensive fruit damage had occurred. This suggested that either the pheromone itself was not attractive to our population of male CFW, or that the timing of pheromone trapping activities did not coincide with male moth flight.

The objectives of our study were to compare the attractiveness of 4 different commercially available pheromone lures to adult male CFW and to monitor flight phenology. Eric LaGasa at the Washington State Department of Agriculture found that traps baited with false codling moth and European grape berry moth lures had a noticeable bycatch of CFW. This information was used to select the pheromones for the study. The lures used were as follows: false codling moth (Thaumatotibia leucotreta), European grape berry moth (Eupoecillia ambiguella); cherry fruitworm (Grapholita packardi), and a control.

Pheromone traps were set up from May 11 to July 27, 2012 in the Abbotsford blueberry field with a known infestation of CFW.  Sticky wingtraps were baited with one of the four commercial pheromone lures. Treatments were replicated 8 times. The traps were checked weekly, and lures were replaced every four weeks.

[blockquote style="1"]The results showed that the false codling moth lures attracted significantly more male CFW moths than all the other lure types. The maximum weekly CFW catch for a single false codling moth trap was 76 males. The maximum weekly trap catch for a single trap in any of the other treatments was 2 males.[/blockquote]

Male CFW moths were caught in false codling moth traps in all weeks of trapping from May 11 to July 27. Trapping indicated three peaks in adult CFW flight: May 25-June 1, June 15-22, and June 29-July 6. These results suggest that the period of CFW flight in our region is similar to that in Michigan, with flight beginning in early May and continuing into early July. Based on the flight phenology observed in this study, the window for insecticide applications at the research site was likely within the first 3 weeks of June.

Area-wide surveillance trapping for cherry fruitworm was continued during the summer of 2013 and results of this work will be compiled in early 2014.

Funding for this study was provided by the BC Blueberry Council. E.S. Cropconsult would like to thank Tracy Hueppelsheuser from the BC Ministry of Agriculture for her input on this project. 

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