July 31, 2009
(Red Deer, Alberta) – The yellowheaded spruce sawfly is taking its toll on Red Deer spruce trees, and controlling the pest during the next two weeks is crucial to stopping its spread.
The pest has been present in Red Deer for several years, and populations continue to grow. According to Elaine Johnson, Urban Forester for The City of Red Deer, the yellowheaded spruce sawfly is especially bad in the newer areas of the city.
“The sawfly favours young trees, so neighbourhoods such as Inglewood, Kentwood, Johnstone Park and Johnstone Crossing are being hit particularly hard,” said Elaine Johnson, Urban Forester for The City of Red Deer. “The sawfly presence is also strong in Edgar Industrial Park. They are damaging trees throughout the city, but those areas are where we’ve seen the highest populations.”
Citizens who see sawfly larvae on their trees can deal with them in one of a few simple ways. The larvae are easy to spot while examining your spruce trees; larvae range in size from a few millimeters to an inch long, resembling small green caterpillars. Their heads are yellowish-brown and they have grey-green stripes running the length of their bodies. They usually feed first at the tips of branches on new foliage, moving on to older foliage subsequently.
Larvae can be picked by hand from trees or property owners may prune the tips of branches where they find the larvae feeding. Larvae and pruned tips should be disposed of in sealed garbage bags. Sawfly larvae may also be blasted from trees with a high-pressure water spray; small larvae will not be able to crawl back onto the tree, but later stage larvae may be able to if they are not disposed of after spraying.
“The yellowheaded spruce sawfly will continue to re-infect trees each year until the tree is defoliated,” said Johnson. “Conifers such as spruce trees cannot withstand severe defoliation and will die as a result of losing their foliage. Our trees are a treasure that we can’t afford to lose, and dealing with the sawfly now is the only way to stop its spread to more Red Deer trees.”
The sawfly has one generation per year. It overwinters as larvae in soil-encrusted cocoons beneath trees. It attacks Engelmann, white, black, and blue spruce. Damage may only appear on sections of the tree, but repeated attacks of the yellowheaded spruce sawfly severely retards the height and radial growth of the tree and will eventually kill the tree if not controlled.
For chemical controls of the yellowheaded spruce sawfly, contact your local garden centre or pest management companies. For more information on management of this and other harmful tree pests, see www.reddeer.ca/parks or call Parks Forestry staff at 403-342-8344.
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For more information, please contact:
Elaine Johnson
Urban Forester
The City of Red Deer
403-348-7416
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