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 …
Douglas fir beetles may be wreaking havoc on their pine-tree victims, but the insects can be fooled so trees in the Shoshone Forest’s developed areas can survive the beetles unscathed.
Since around 2000, 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 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.
The MCH capsule looks like an Alka-Seltzer tablet encased in a chocolate brown shrink wrap. The bags are stapled to the tree above eye level.
In the Newton Creek campground on the North Fork of the Shoshone River, Allen stapled the packets to Douglas fir trees on April 26. It was cold, but beautiful at the campground, with pine trees swaying soothingly in the wind amid a few scattered snowflakes. The stately, towering trees appeared healthy.
“I’ve been amazed at how well it works,” Allen said of MCH.
But the Shoshone Forest is a big place and not every tree can be treated.
Because only 15 percent of the Shoshone Forest has roads, protecting trees from beetles has been a challenge. In campgrounds and other developed sites, trees are considered “high value” for their aesthetics, so Shoshone Forest personnel are able to take a proactive approach to treat them with MCH or spraying them with Carbonyl, an insecticide, to prevent beetle attacks, Brey said.
“In most other areas of the forest we have not been able to keep pace with the beetles, and so we are left to do salvage logging sales where we remove mostly dead and dying trees,” Brey said.
In a perfect world, timber harvesting could be conducted before the onslaught of beetles. By thinning trees, the remaining healthy trees are more resistant to beetles, Brey said.
Meanwhile, picturesque stopovers like Newton Creek campground can be preserved.
The service’s short-term goals are to remove hazardous trees in campgrounds and other public areas. The short- to mid-term goals are protecting high-value trees, and for the long term, service employees want to craft management plans for campgrounds and encourage growth of young trees, Brey said.
Almost all the trees in Newton Creek are tall, as though they’ve been guarding tents and campers for decades.
Successfully planting saplings is difficult in high-traffic areas, Allen said.
Even with MCH, Douglas fir trees are not out of the woods.
“The North Fork has been hammered pretty heavily by Douglas fir beetles, spruce beetles and mountain pine beetles,” Brey said.
But Douglas fir beetles are the biggest problem because the North Fork has a lot of Douglas fir, Brey said.
Douglas fir beetles began their North Fork assault in the 1990s, resulting in a long-running beetle epidemic. Usually fir beetles run their course in two or three years, Allen said.
Of the 2.2 million acres comprising Shoshone National Forest, 925,000 acres have been impacted to some degree by beetles, according to figures provided by Bryan Armel, natural resources staff officer for Shoshone Forest.
That is a large area, but the numbers are based on aerial surveys. Listing a forest area as impacted could mean an entire swath of forest is dead, or that a few trees scattered throughout a given area have been killed, Brey said.
Still, considering 1.3 million acres of that 2.2 million acres is forested, 925,000 is a large chunk.
“That’s over 70 percent,” Brey said.
Because they have about eaten themselves out of house and home, Douglas fir beetles are starting to wind down along the North Fork, Brey said. Now, the beetles are moving to the Clark’s Fork and Sunlight areas, Allen said.
“Up in the Clark’s Fork, they’ve really picked up steam the last couple of years,” Allen said.
Insect outbreaks are a natural occurrence, but the scale of the attack is unlike any previous outbreaks, Brey said.
“We may not know the Shoshone as we once did in certain areas because of the beetle, but with death, a new forest is born,” Brey said. “Many forest stands have advanced regeneration in the understory (vegetation usually found beneath the trees) to take the place of the dying mature trees.”