For the week of March 19 - 25, 2003

Mountain pine beetle munches SNRA trees

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By GREG STAHL
Express Staff Writer

The mountain pine beetle, a tiny insect about the size of a grain of rice, is killing thousands of acres of trees in the Sawtooth National Recreation Area as well as other areas of Idaho and the Pacific Northwest.

"This mountain pine beetle is probably the most powerful insect we deal with in the Northwest, in that it probably has the potential to kill more trees than any of the bark beetles we deal with," said Forest Service entomologist Ralph Thier. "It’s not anything new. It’s a native insect. It has a full complement of prey species and predators. This is what it does."

Mountain pine beetles, though always present in lodgepole pine ecosystems, began attacking lodgepole pine trees in the Salmon River canyon at an elevated pace about six years ago. Since then, the insects swept upriver and moved into the Pettit and Alturas lakes region of the Sawtooth Valley. The numbers of trees killed is approaching levels that haven’t been attained since 1977 when about 200,000 trees were killed in one year. In 2001 the beetles killed 60,000 to 70,000 trees, but that figure jumped dramatically. Last year, the beetles killed 845,000 trees.

"We are experiencing an epidemic attack of mountain pine beetle," said SNRA Area Ranger Deb Cooper. "The result is an accumulation of hazardous fuels. We are very concerned about this buildup of dead material, particularly in and near areas where wildlands interface with homes and developed recreation sites."

Though mountain pine beetles are a native part of the ecosystem, measures must be taken to reduce fuel loading and to save specimen trees in selected areas, forest managers said.

Mountain pine beetles attack living trees and build egg galleries beneath their bark. When eggs hatch, the larvae chew feeding channels to the cambium layer of the tree, effectively girdling the host.

Thier said mountain pine beetles are always present in the forest.

"However, when trees are weakened from things like extended drought, or have reached and exceeded maturity, they are prime targets for attack by insects."

The infestation under way on the SNRA is much more significant than the one in the mid-1980s. In some areas, more than 70 percent to 80 percent of the trees are dead or dying.

"With respect to the current infestation, there are still a lot of potential host trees for the beetle in this area," Thier said. "A lot more trees are going to die. I think this thing’s going to continue to roll."

 

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