Cover Story
Clearwing infestation expanding
Growers can help efforts to stop the spread by checking surveymaps that indicate populations of this invasivemoth in their area.
By Judie Steeves T
he pest is particularly insidious because it can be lying in wait in your orchard, undetected, for years, before you notice that a tree just doesn’t look healthy — and by then, it’s too late.
Such is the nature of the Apple Clearwing Moth, a non-native pest of apple trees that was first detected in the Similkameen in 2005, but which entomologists believe was likely there at least five years earlier.
A detailed survey of apple orchards throughout the Okanagan and Similkameen last year headed up by entomologists Hugh Philip and Gary Judd, in collaboration with the B.C. Fruit Growers' Association, the Okanagan-Kootenay Sterile Insect
Release (OKSIR) program, the B.C. Tree Fruit Co-op and the provincial agriculture ministry, showed an exponential expansion of infested acreage from the last survey done in 2012. The survey involved OKSIR staff setting monitoring traps in all apple blocks in the Okanagan for the summer, then gathering them up and having a specialist record the data from them in the fall. Maps detailing the findings of this survey
Tamara Richardson of Cornucopia Crop Consulting has been hired to work with growers one-on-one and in small groups to help them try and prevent the spread of Apple Clearwing Moth.
and that of 2012 are available for orchardists to view, on the OKSIR website at:
www.oksir.org/maps.asp Once you’ve located your
neighbourhood, you can focus on your orchard and see how many ACM adults were counted in it last year, along with learning, by the colour code whether there were any there in 2012. Even those blocks that are clean and green on the map could already be infested, because the insect takes two years feeding under the bark of the tree, from egg to adult. Only adults were counted, but orchardists who see yellow, brown or red on the map of their neighbourhood know they are already under threat and that they need to be working with their neighbours to take precautions to ensure the pest does not spread. Philip notes that the female moth looks for breaks or crevices or pruning wounds in the bark of the tree in which she will lay her eggs. Cankers and grafted unions are also vulnerable sites for egg-laying.
The insects attack all ages of trees that have suitable egg-laying sites.
Gary Judd
Because it’s an invasive pest, the apple clearwing doesn’t have a lot of natural enemies. Once an orchard is infested, the moths will thrive and develop quickly. To prevent them from spreading, don’t move trees from an infested area to a new
area, Philip advises. Trees removed from the orchard should be chipped or burned by late spring, before the next generation appears.
Infested trees will have reduced vigour; branches may die and fall off; and the tree is generally in a
weakened condition so it is pre-disposed to attack by other insects, he explains. Mating disruption can be used to help suppress moth
Hugh Philip British Columbia FRUIT GROWER • Summer 2015
populations, as well as mass trapping, so long as populations are not
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