Spruce budworm eat the needles of Douglas-fir trees. (Bill Ciesla)

In the Clarks Fork area of the Shoshone National Forest, towering evergreen trees stand like skeletons, naked and needleless. The greenery is gone, transformed to what Kurt Allen, an entomologist with the Forest Service, describes as a gray, “ghost forest.”

The trees, some dead, and some still struggling to survive without needles, are victims of what Allen calls “the most bizarre” spruce budworm epidemic he’s ever seen.

Spruce budworms, despite their name, mainly attack Douglas-fir trees. The insect, which eventually transforms to a gray moth, is native to Wyoming and about every 20 years appears in epidemic proportions.The last big outbreak on the Shoshone was in the mid-1980s.

So Allen wasn’t concerned when about four years ago he saw small stands of needleless trees.

Spruce budworm are killing trees on the Shoshone National Forest. The insects feed on tree needles. (Kurt Allen)

Spruce budworm winter in the trees and emerge in the spring and feast on tree needles. A tree’s needles catch the sun, which allows it to make the sugars that feed the roots and keep it alive, Allen said. In Wyoming, in particular, May, June and July are prime food-making months. It’s also when spruce budworms are most active.

The trees go into survival mode when they lose needles, Allen said. A tree can rebound from one year without needles, even two years.

The problem with this epidemic, Allen said, is that has lasted more than three years, much longer than normal. “Trees are living critters, too,” he said. ”They do need food and water at some point.”

More than a typical epidemic

Spruce budworms have impacted tens of thousands of trees and up to 15,000 acres on the Shoshone since Allen first noticed the outbreak about four years ago. Spruce budworm use silk thread to float tree-to-tree, usually feasting on shorter trees.

“The thing that is striking and really sort of concerning about what is happening, is that even the big trees are getting stripped of all their needles, which is something we don’t see happen very often,” Allen said. “It’s the worst I’ve ever seen budworm behave. Last year and this year it seemed to have ramped up to a place where even those big trees with the giant crowns have no needles on them.”

Spruce budworm grow into gray moths. They are native to Wyoming, but the Shoshone National Forest is experiencing a particularly bad outbreak of the insects. (Bill Ciesla)

Also odd is how localized the outbreak has stayed. So far, only the Clarks Fork area of the Shoshone has been impacted.

Although the affected area is comparatively small, it comes after years of devastation caused by the decades’ long pine beetle epidemic that denuded mountain slopes and killed millions of  trees in Wyoming alone.

Like the pine beetle infestation, the budworm epidemic has aesthetic as well as touristic consequences. The main budworm outbreak is along the popular Chief Joseph Scenic Byway north of Cody. The Forest Service is concerned with forest health, but also maintaining the aesthetics of the byway, said Kristie Salzmann, spokeswoman with the forest.

Allen doesn’t know why the outbreak has been so severe this time, or why it’s stayed in one hotspot. What he does know is that thousands of trees have already died and those still surviving in the area won’t last much longer if the budworm attacks keep occurring.

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Staff on the Shoshone are planning to thin the area and remove dead timber to help mitigate the epidemic, Salzmann said.

The agency held a public meeting in early September in Crandall to talk about vegetation management and the outbreak. The Forest Service plans to release a report in the next few weeks that will outline a plan of attack. Salzmann said she didn’t yet know specific numbers, but the plan will include thinning and timber sales. It does not call for any spraying for the budworm. People will have 30 days to comment on the scoping document once it is released.

Kelsey Dayton

Kelsey Dayton is a freelancer and the editor of Outdoors Unlimited, the magazine of the Outdoor Writers Association of America. She has worked as a reporter for the Gillette News-Record, Jackson Hole News&Guide...

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