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For the week of July 11 - July 17, 2001


Lodgepole pine face epidemic

Mountain pine beetles sweep through SNRA

Express Staff Writer

A slowly advancing wave of death is rolling across portions of the Sawtooth National Recreation Area.

Mountain pine beetles have decimated lodgepole pine forests in the Salmon River Canyon and on several of the Sawtooth’s glacial moraines and hillsides. Red-brown pine needles and dead trees are left in their wake.

"It has really kind of exploded in the past few years," SNRA Forester Jim Rineholt said. "Many people think it’s not a natural process, but it’s really a natural process at work."

The dead trees the beetles leave behind are excellent habitat for woodpeckers, including several sensitive species that call the SNRA home, SNRA Biologist Robin Garwood pointed out. Additionally, the beetles leave behind fire-prone tree skeletons, which, when they burn, help renew the life cycle for an entire lodgepole forest.

Rineholt said the beetles usually attack 8- to 12-inch diameter trees that are 80 years or older.

"They like to hit the larger, more mature trees because they have more food for them," Rineholt said.

The beetles have killed more than 4,000 trees in SNRA campgrounds, alone. Numbers of dead trees on the SNRA as a whole are more appropriately measured in acres rather than trees, because so many have fallen prey. On the SNRA, about 7,000 acres of lodgepole pine trees are or have been infested. That translates to more than 26,000 trees, Rineholt said.

Mountain pine beetles are the "most important native bark beetle pest of mature pines in the Western United States," according to a Forest Service information pamphlet. "Epidemics can build rapidly and kill hundreds to millions of mature trees each year."

Mountain pine beetles experience four life stages: egg, larva, pupa and adult. The beetles have one generation per year and typically take one year to complete a life cycle. Most spend winters as larvae, when they eat, and kill, host trees. Adults emerge from host trees and infest others during July and August.

The effects of beetles’ feeding is not apparent until the summer following an infestation.

Female beetles initiate the attacks when they lay up to 48-inch-long "galleries" of eggs beneath a tree’s bark.

The spring after a tree has been successfully attacked, it begins to fade. Foliage typically turns yellowish, then red-orange, and finally red-brown. After two or three years, most needles fall from a dead host tree.

To avert the beetles’ damage in campgrounds and highly visible areas, the Forest Service is using an insecticide called Carbaryl, which can prevent a tree from becoming infested.

The Forest Service must adhere to strict guidelines when using the insecticide. Because Carbaryl can be fatal to all insects, including those in rivers, it cannot be sprayed within 50 feet of a stream or river, or during heavy winds.

But many of the SNRA’s forests will remain unprotected, while the natural process continues.

"One thing we know about the Sawtooth Valley is there’s no shortage of mature, good-size lodgepole pine," SNRA Recreation Specialist Lisa Stoeffler said.

"I think they’re going to go pretty strong here for the next couple of years," Rineholt added.

The Idaho Mountain Express is distributed free to residents and guests throughout the Sun Valley, Idaho resort area community. Subscribers to the Idaho Mountain Express will read these stories and others in this week's issue.