Apr 25, 2012 - The Associated PressPOWELL (AP) -- The pine beetle infestation in Shoshone National Forest appears to be subsiding.
Forest timber program manager Randy Spiering says the beetles may be running out of host trees and a freeze in October 2010 killed many beetles before they could protect themselves from the cold.
Officials have observed that the acreage of trees with Douglas fir, spruce and mountain pine beetles decreased last year.
Trees with spruce bud worms increased, but spruce bud worms usually don't kill trees.
Shoshone Forest totals 2.4 million acres. Some tree stands remain unscathed, while others are clearly ailing from beetle infestations.
Last year, forest managers had some success in tricking the insects into leaving healthy trees alone.
Douglas fir trees in campgrounds along the North Fork of the Shoshone River have been treated with methylcyclohexanone, or MCH, said Kurt Allen, etiologist for the U.S. Forest Service in Rapid City, S.D.
Douglas fir is one of the primary conifers in the Shoshone, said Jason Brey, Silviculturist for the Shoshone.
Douglas fir beetles communicate to other beetles with chemical messages called pheromones. An anti-aggregation pheromone dispatch can signal other beetles that the tree is full. This chemical, MCH, has been synthesized to trick beetles into believing the tree is at beetle capacity so they don't invade beetle-free trees.
Douglas fir beetles prefer trees that are injured or have died recently, but when there are lots of beetles, they will attack healthy trees.
By assaulting in large numbers, the beetles can kill the tree, said a U.S. Department of Agriculture report that described the chemical. Hundreds of thousands of beetles will hit one tree, Allen said.
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