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Pest Management

Tree killer spreading rapidly

Group effort by growers seen as best way to control ClearwingMoth. By Judie Steeves


he extent of the spread of Apple Clearwing Moth throughout the Okanagan Valley has been a

surprise, says entomologist Gary Judd, a research scientist at the Pacific Agri-food Research Centre in Summerland, who conducted a comprehensive study last summer. He set out traps in every block of orchard from the U.S. border to Salmon Arm in the Okanagan and created maps showing the pest’s presence and in what numbers. The moth first appeared in orchards in the Similkameen in 2005 and today the area is generally infested with the borer, which damages trees by feeding under the bark during its larval stage. The detailed maps are available on

the website of the Sterile Insect Release program at Judd speculates the moth may

move on vehicles or in trees that are being moved, not just by flight. “Soon it will be everywhere,” he


Orchardists such as Denise MacDonald of Summerland say the worst of this pest is that it kills trees, not just destroys the fruit, so growers lose their capital investment, rather than just a year’s crop, when it moves in. It takes four or five years before a

new tree begins to crop, then several more years before a full crop can be harvested—and all of that is lost if a tree dies. Growers have been advised to

British Columbia FRUIT GROWER • Fall 2013 23

monitor for the Clearwing using traps, and if there are one to 50 moth captures, to use mating disruption to control it. However, when levels get too high, Judd says mating disruption no longer seems to work for control. Instead, the trunk of each tree

must be sprayed, which is an expensive and labour-intensive process. Control is best done by whole neighbourhoods rather than a single property owner because the moth can travel easily from one to the other, negating efforts by a single grower. Some growers are seeing damage

to their trees, but Judd says others aren’t seeing much, which makes it difficult to assess the economic impact of the new pest. He suspects it arrived in North

America in material imported from an infested area. The B.C. Fruit Growers’ Association is preparing a funding request to implement a three-year, area-wide pilot project, in cooperation with the SIR program, to evaluate the effectiveness of mating disruption for control, says general manager Glen Lucas. However, the SIR program’s board

needs to be notified by the end of 2013 in order for staff to be hired for next year. Growers are encouraged to examine the area maps to see what the new pest’s population density is like in their area and to determine the best method of control to use. The new dwarf trees are more affected by clearwing moth than the old, larger type of apple tree Judd said.

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