Foreign insect attacking Idaho evergreens

KETCHUM, Idaho – A non-native insect is attacking pine trees in the central Idaho resort area of Ketchum and could wipe out all the blue spruce trees in the Wood River Valley.

The small insects, called pine needle scale, appear as white dots on pine needles. The insects suck water and nutrients from the needles, causing the needles to turn brown and die.

“Pine needle scale is widespread here in the Wood River Valley,” said arborist Bill Josey, owner of Arbor Care Resources Inc. “It is especially bad in the older, more established neighborhoods like Hulen Meadows, the Sun Valley Fairways and Elkhorn.”

The insects mainly go after Colorado blue spruce, a non-native plant brought to the region for landscaping. The non-native insects came with the spruce, and have no natural parasitic wasps to control their population.

“In west Ketchum, if this is not addressed, it could wipe out all the spruces in the valley,” Josey said.

Jim Rineholt, forester with the Sawtooth National Recreation Area, said the insects have been hitting most evergreens in the area, not just blue spruce.

“We are definitely starting to get a lot more calls on the subject,” he said.

Josey said the pine needle scale infestation has worsened as it has gone unnoticed and untreated for years, allowing the insects to reproduce. He also said additional development in the region has decreased open spaces between neighborhoods, making it easier for the insects to infest more trees.

The insects hibernate during the winter. In May and June, eggs hatch, and the insects move more actively, spreading in branches and moving to new trees. Female scales lay about 40 to 100 eggs.

Josey said trees can be saved with a series of treatments if the insects are spotted early.