Pine beetle infestation killing off trees in West

Amy Gannon, hatchet in hand, sliced a slab of bark from a lodgepole pine tree near Wolf Creek, Mont., and quickly spotted a mountain pine beetle larva no bigger than her pinky fingernail.

"This tree's done for," said Gannon, an entomologist with the Montana Department of Natural Resources and Conservation.

As wildfires roar through tinder-dry forests in California, the mountain pine beetle is silently killing even more trees — hundreds of thousands of acres of towering trees, mostly lodgepole pine, according to Robert Mangold, director of Forest Health Protection for the U.S. Forest Service.

An epidemic of this magnitude hasn't been seen in the Mountain West in 25 years, he said.

In 2007, the beetles were blamed for killing 3.9 million acres of trees in Colorado, Montana, Wyoming, Oregon, Idaho, Utah and Washington, Mangold said.

By comparison, the fires in California had burned 640,847 acres as of July 14 this year, according to the National Interagency Fire Center. An average of 3.4 million acres has burned nationally each year since 2003, according to the center.

The current pine beetle infestation is the worst since 1981, when 4.7 million acres of trees were infected, Mangold said. He blames the outbreak on a perfect storm of drought, large stands of old trees and, possibly, warmer temperatures because of climate change.

"It's shocking," said Jeff Witcosky, an entomologist for the U.S. Forest Service in Lakewood, Colo. "We talk about the grieving process."

While the impact has been enormous, Mangold said, the mountain pine beetle is a native insect that, along with fire, does play a role in the regeneration of lodgepole pines.

The pines have a hard cone that won't open without a hot fire, he said. When the cones open, they dump out seed, creating a thick forest of trees of the same age. When the trees hit 80 to 90 years old, they weaken and become susceptible to the mountain pine beetle. The beetles kill the trees, creating more dry fuel for those fires, he said.

This month, the adult beetles are emerging from trees and looking for hosts they can bore into to mate and lay eggs, Gannon said. The beetles feed on the inner bark, severing the tree's circulation, she said.

The large number of affected acres is increasing the risk of large fires as the Northern Rockies enters the fire season, said George Weldon, deputy director of fire, aviation and air for the U.S. Forest Service's Northern Region.