Forest Service keeps tabs on bugs that threaten fir forests

LEWISTON, Idaho — State and federal entomologists are tracking the spread of a tiny invasive insect that feeds on fir forests.

The Lewiston Tribune reports the Idaho Department of Lands says the balsam woolly adelgid has the ability to rearrange the species composition of Northwestern forests, and it’s already been found in northern Idaho.

The wingless insect is from Europe and was first introduced to North America in the early 20th century. With no native predators, the bug has flourished.

“There is not a very effective group or guild of predators that feed on this insect,” said Tom Eckberg, an entomologist and forest health program manager for the Idaho Department of Lands at Coeur d’Alene.

Eckberg said the bugs, which are about 1 millimeter long, can quickly kill any member of the true fir family, which excludes Douglas fir. A U.S. Forest Service pamphlet on the bug states that in some areas “firs are slowly being eliminated from the ecosystem; and adelgid populations continue to spread to previously uninfested areas.”

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“They tap into the vascular system of the tree, and they will suck out juices and liquid and also inject toxic saliva which causes abnormal cell growth,” Eckberg said. “It causes the wood to grow abnormally and interferes with transport of nutrients. Over time, it can disfigure the branches.”

The bugs have been documented in the Potlatch River drainage in the Clearwater Basin. They produce waxy, wool-like threads for protection that can look like a white fuzz when adults congregate on trees.

“It can kill a tree, sometimes in three years or so,” Eckberg said.

Cold winters can check the spread of the bug because they are prone to temperatures below 30 degrees. But deep snow can insulate the insects and keep them from freezing.

Chemical treatments can kill the bugs on urban landscaping, but they aren’t economical for use in vast fir forests.

Entomologists are tracking the insect’s spread to help foresters understand which areas may be at greatest risk for infestation and how forests may change in the future. The surveys can also inform their decisions about future forest management.

The monitoring effort began in 2008, when forest scientists established survey plots which they re-visit about every five years.

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Information from: Lewiston Tribune, http://www.lmtribune.com

The Associated Press