Doing battle with bark beetles

Pheremones being used to treat Lake Wenatchee outbreak

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LAKE WENATCHEE — A December 2012 storm in the Lake Wenatchee area that toppled perhaps thousands of trees, closed roads and cut power to some areas for more than a week is still wreaking havoc. This time, it’s in the form of bugs.

The large number of dead and dying trees in the area has spurred an outbreak of Douglas fir bark beetles, said Don Youkey, wildlife biologist for the Wenatchee River Ranger District.

Concerned about a mass attack by these beetles in certain areas, the Okanogan-Wenatchee National Forest last week treated some 250 acres along the Little Wenatchee River Road, he said. The Glacier View and Nason Creek campgrounds and an area along the south shore of Lake Wenatchee are also being treated, he said.

What they’re putting out is not poison. Not to humans, or to the bugs. Known as an anti-aggregating bark beetle pheromone, the pouches they put out and staple to trees contain a natural substance secreted by the beetles.

“What happens is pretty interesting,” Youkey said. “If they mass attack a tree, they put out this pheromone that says, ‘Hey, this site’s full. Go find your own tree.’ ”

The pheromone has been around since the late 1990s, and is often used to control overpopulation caused by major disturbances, such as windstorms, floods and fires, said Connie Mehmel, regional entomologist for the Okanogan-Wenatchee National Forest.

But it must be put out at the right time — just before the beetles emerge and start to fly. Once they’ve attacked a tree, it’s too late for the pheromone to repel them.

“It’s been kind of a godsend to forest entomologists,” Mehmel said of the pheromone. “It only works for one type of bark beetle — the Douglas fir bark beetles — but it works really well,” she said, adding, “It’s kind of a magic bullet.”

She said the Forest Service is watching for other outbreaks in the area due to the weakened state of many trees.

Youkey said Douglas fir bark beetles selectively attack large firs, so the agency is trying to protect what’s known as a late successional reserve in the area. The reserve of older trees is prime spotted owl habitat, he said. For safety reasons, the Forest Service wants to protect large trees in campgrounds and areas around homes on leased property by the lake.