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Invading European Insects Appear In Utah's Forests

Fir tree suffers from Adelgid infection
William M. Ciesla
Forest Health Management
Effects of the Adelgid include the swelling of tree branches




People aren’t the only ones active this summer. Small insects are also out and about, taking advantage of the warmer weather and green real estate.

The Balsam Woolly Adelgid is an insect of European origins. It gets its name from its somewhat fuzzy appearance when groups of it are found on trees. It was introduced in parts of North America during the 1900s. Presumably hitchhiking on nursery stock and other transported goods.

“Throughout the last century it’s made its way around and finally now it’s hit Utah,” said Ryan Davis, an entomologist with Utah State University Extension.

The non-native adelgid is impacting subalpine fir trees across Utah. Davis describes some of the signs of an affected fir.  

“We look at the ends of the branches and we see the swellings. They call them gouting, and that is a reaction of the tree from the feeding that has occurred,” Davis said.

The reaction is not so different from a human.

“It’s what we call hypersensitive response, you can almost think of it as an immune response, it causes the tree to produce these larger than usual cells and it actually then will inhibit the trees ability to transport nutrients and water,” Davis said.

Davis works in the Plant Pest Diagnostic Lab and says pesticides and tree removal are the only way to treat the Adelgid. While it is unlikely to see this pest around town, because it prefers higher elevation subalpine environments, another pest that may start appearing is the Elm Seed Bug.