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Colorado: Bark beetle outbreak slows

Bugs killed up to 80 percent of mature trees in heavily hit areas; foresters emphasize removal of dangerous trees and proactive management to ameliorate future outbreaks

Most new pine beetle activity in 2011 was in Larimer and Boulder counties.

SUMMIT COUNTY —Pine beetle activity for the most part has died back down to background levels, with a few hotspots in Tenmile Canyon and in the high-elevation fringes of the lodgepole zone, according to results from the latest aerial surveys of Colorado forests.

The survey confirms that the bark beetle epidemic has slowed dramatically west of the Continental Divide. Forest and insect researchers have attributed the decline to several factors, including generally wetter conditions the past few years that have enabled some trees to repel the bugs. And, in some area, the beetles have already killed most suitable host trees, leaving nowhere else to reproduce.

Bark beetles are active in mid-summer, when they emerge from beneath the bark of infested trees. fly to new hosts and lay eggs. The larvae then burrow beneath the bark, spreading the blue-stain fungus that kills the trees within a year.

Bark beetle activity has slowed in Colorado, but tripled in the Black Hills of South Dakota in the past few years.

Since the first signs of the outbreak in 1996, the bugs have killed 3.3 million acres of trees in an epidemic that’s unprecedented in the modern era.

Agency leaders continue to emphasize removal of dangerous dead trees and are advocating for proactive forest management to prevent a similar outbreak in the future.

“Our actions today and in the future will shape forest conditions for the next 100 years or more,” said Jeff Jahnke, state forester and director of the Colorado State Forest Service. “Active forest management on both public and private lands can lead to healthier trees on the landscape and create the diversity necessary to reduce future large-scale insect epidemics. If we don’t plan now for ongoing management of these forests, we will set the stage for another mass disturbance like the current bark beetle epidemic.”

“Protecting the public, our employees and critical infrastructure remains the highest priority for the U.S. Forest Service,” said Maribeth Gustafson, acting regional forester for the U.S. Forest Service, Rocky Mountain Region. “Our efforts are making a big difference on the ground, but there is still a lot of work to be done.”

For the first time, spruce beetles took a greater toll on the forests than mountain pine beetles. The U.S. Forest Service and the Colorado State Forest Service reported a total of 2622,000 acres of tree mortality related to spruce beetles, mainly in southwestern Colorado, but also moving northward toward the Gunnison area — not too far from the southern edge of Eagle County.

Since 1996, spruce beetles have affected more than 1 million acres across Colorado. Spruce beetle populations are rapidly expanding in some areas causing entire drainages to be infested in the course of one year. In some cases nearly every mature spruce has been killed in multiple drainages, from the creek bottoms all the way up to the high elevation krummholz.

Spruce and fir forests in Eagle County that could be affected by spruce beetles include high-value stands including the Back Bowls at Vail, where White River National Forest rangers previously advocated for proactive treatments to increase age-class diversity.

Pine beetles killed another 140,000 acres of trees across the state in 2011. Larimer County was most affected by the spread in both lodgepole and ponderosa pine stands.

Pine beetle activity has tripled in the Black Hills area of South Dakota during the past three years.

In the Rocky Mountain Region, Forest Service crews and contractors removed dead trees along 275 miles of roads and 162 miles of trails. An additional 12,000 acres of hazardous fuels within the wildland-urban interface and adjacent lands were cleared of beetle-killed trees.

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2 Responses

  1. I suppose they remove them in some cases, but in many others the trees are just felled and left to lie. A whole lot uglier than when the dead trees were standing. I noticed that in the recent big windstorm as many live trees as dead ones fell over. But my evidence is just anecdotal, so hopefully all their effort is doing something useful.

    • They can’t really remove all the trees from trails and such … too expensive. Most of the dead ones will fall over at some point, but I agree with you; there was a sort of spooky beauty to the standing dead forests. And, yes, the live trees that are left are much more susceptible to wind.

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