Spruce budworm outbreak threatens Douglas fir in Shoshone National Forest

Wyoming’s mountain pine beetle epidemic has finally subsided – but now another insect is causing “great concern” in the state, forest officials said this month.

The Western Spruce Budworm is a “defoliator that attacks the needles of Douglas fir,” putting the tree under “extreme stress” and even killing the tree “in a lot of instances,” state forester Bill Crapser told the Joint Agriculture, State, and Public Lands and Water Resources Committee during a meeting June 6.

The budworm is “really prevalent” in the southern Bighorns, he said – but it’s also been spotted in the Wind River Mountains.


Crapser’s written report indicates the northern and southern ends of the Shoshone National Forest have experienced budworm defoliation.

The insect has also appeared in the Bridger Teton National Forest, in “some places on Pole Mountain, and over into the Snow Range,” Crapser said.

“We’re seeing a lot of spruce budworm,” he said. “(It) appears to be on the increase in many areas.”

This figure shows the total recorded acres damaged by western spruce budworm, by year. Survey coverage was reduced in 2020, officials said, explaining the reduction in acreage recorded that year. h/t Wyoming State Forestry Division

He described one location that might be familiar to motorists commuting between Laramie and Cheyenne.


“As you go over the summit and down through Telephone Canyon, on the south side of the highway that north-facing slope is all Douglas fir,” Crapser said. “You’ll notice it’s pretty gray. … It was heavily impacted with spruce budworm.”

Forest officials have “done a lot of burning” in the area to try to alleviate the problem, he said.

They also tried to thin the trees from below to give them “more vigor to fight off the budworm.”


Crapser called it the “only treatment we could really do (to) save those trees.”

His report indicates budworm outbreaks can be “long-lasting.”

Wyoming’s has lasted three years so far, according to a Bureau of Land Management official who also spoke during the meeting.


Forest recovery

Now that the mountain pine beetle epidemic – which also impacted the Shoshone National Forest – has subsided, Crapser said forest officials are working on a plan to revitalize lodgepole and ponderosa pine forests across the state.

“We’re really looking at more of a forest recovery,” he said. “(We’re deciding) what do we do next – what type of management do we do in those forests.”

For more information contact the Wyoming State Forestry Division.


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