Whitman County’s wheat fields generally escape being hit by the invasive insects that typically cost Washington state’s economy $1.3 billion a year. But other species of invasive insects do sometimes plague the Palouse.

That’s the take of Stephen Van Vleet, an educator with the Whitman County Washington State University Extension office.

Even though insects usually leave grain alone, pine beetles sometimes infest stands of evergreen trees that dot the Palouse hills, especially in drought years.

“It kills the tree from the top down,” Van Vleet said.

Trees that have been hit have masses of sap 4 to 7 feet up their trunks.

“(You) won’t see the beetle,” Van Vleet said. “It’s very, very small.”

After a tree is attacked, an insecticide can be applied.

“It’s very expensive,” he said. “Unless it’s your favorite tree, you’re wasting your money.”

Often, after pine beetles attack, another wave of insects called red turpentine beetles follows, leaving what appears to be sawdust at the base of trees. At that point, the trees can’t be saved.

A better approach is to make sure trees are getting enough water, which makes them less vulnerable to pests.

While the forests in Whitman County are too small to be a major factor in the wood products industry, the beetles create expensive issues. The loss of trees can reduce property values by making home sites less scenic. Dead trees that aren’t removed can provide fuel for wildfires that can damage homes or fields, Van Vleet said.

Because of the threat invasive insects pose, the Washington Invasive Species Council recommends homeowners check their trees and swimming pools for signs of infestations.

If they spot anything unusual, they can take photographs and report their findings at invasivespecies.wa.gov/report.shtml

A Washington state study found that, since 1990, at least 70 new insect species have been detected in the state, according to a news release from the Washington Invasive Species Council.

“The public found 36 percent of the new insects first, more than formal surveys or regulatory agencies detected,” according to the news release.

Williams may be contacted at ewilliam@lmtribune.com or (208) 848-2261.

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