Cumulative western spruce budworm defoliation in Eastern Washington, 2010-2014. Graphic: Department of Natural Resources / U.S. Forest Service

By Glenn Farley
26 June 2015

NEAR BLEWETT PASS, Washington (KING 5 News) – From the crest of the Cascade Mountains running east to the sagebrush and desert country along the Columbia River, a map shows years of damage from the Western Spruce Budworm, which is killing trees by the thousands.

The state's worst patch of budworm damage is an area bordered by I-90 to the south, as Highway 97 runs right through it.

Moths living in one tree will lay eggs on the tree next to it. And when the caterpillars come out, the damage begins.

"It's a little bit of a zombie tree. It's dead, and it doesn't know it yet," said Aaron Everett, state forester with the Washington State Department of Natural Resources. "They eat the terminal buds, then they eat the new foliage because it's the most nutritious."

The tree starves, as more and more needles fall victim to the caterpillar before it turns into a month. A single infected tree can have thousands of budworms feeding on it. And dead and drying trees are more flammable. The ongoing drought stress in eastern Washington also makes the trees even more vulnerable to bugs.

Everett says the problem is worse in mixed forests of eastern Washington, as the caterpillars go after fir trees: Douglas Fir, Grand Fir, Noble Fir. It does not go west of the Cascade crest, largely because the wetter side of the mountains tends to be too wet and cold in the spring when the caterpillars emerge.

One concern is over a warming climate. If western Washington sees continuing seasons like this one, with drier and warmer springs, "you see potential expansion in those species ranges, if the climate factors that keep them in check are no longer there," says Everett. [more]

Bug infested forests raise fire danger in Washington



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