Beetle infestation at epidemic levels on forest land
Thursday, March 17, 2005
By EVE BYRON – IR Staff Writer – 03/17/05
Bark beetle infestations have reached epidemic proportions within Region 1 of the U.S. Forest Service, with trees on at least 1.6 million acres infected with a number of different types of these bugs. Bark beetles are a natural forest resident and provide valuable services in limited numbers.
But an aging forest and dense tree stands, coupled with recent drought conditions, have led the beetles to multiply to levels that are cutting huge swaths across Idaho, Montana and part of Yellowstone National Park.
Forest Service entomologist Ken Gibson said there’s been some discussion on how to define an epidemic, whether it’s having bark beetles in one tree per acre or in 100 trees per acre. But surveys in Region 1, which includes Montana and portions of Idaho and Wyoming, show that the number of acres with bark beetles has jumped from about 400,000 in 1999 to more than 1.7 million in 2004.
“By almost anyone’s definition, it’s an epidemic,” Gibson said on Friday. “We’re seeing a lot of bark beetle-caused mortality, and what drives that is the stand conditions, overstocking and old age. But the drought is one of the big things that produce susceptible conditions.”
Six different types of beetles are mainly responsible for the dead trees. In particular:
- mountain pine beetles have struck 700,000 acres, hitting various pine trees but focusing about 90 percent on the lodgepole pines;
- Douglas fir beetles have hit about 100,000 acres;
- fir engraver beetles are present on about 300,000 acres, mainly attacking grand fir trees;
- Western balsam bark beetles are eating their way through about 175,000 acres of subalpine fir;
- Western pine beetles are infecting about 10,000 acres of mostly Ponderosa pines;
- and spruce beetles are infesting about 8,000 acres of Engleman spruce.
Generally speaking, the beetles bore into the trees and lay eggs that hatch into larvae and eat the trees, eventually killing them.
The infestations are in pockets of stands throughout the region, but some places have been hit particularly hard. One of the most visible areas is a section of the Beaverhead National Forest along Interstate 90.
“You can see thousands of acres of red trees,” Gibson said. “That’s beetle-killed lodgepole pine. You can also see it in the Lolo (National Forest) along I-90, where there are areas heavily infested.”
Gregg DeNitto, a Forest Health protection group leader in Missoula, added that portions of the Bitterroot and Helena national forests that burned in the wildfires of 2000 also have experienced a lot of beetle killed trees.
“Normally, you would go through a Doug fir beetle outbreak two to three years after a fire, and the infestation has dropped some during the last year or so. But the present drought appears to be prolonging it,” DeNitto said.
Beetles usually play a role in healthy forest ecology, embedding themselves in older trees near the end of their life cycle, which then die and provide habitat for other critters. In fact, Sara Jane Johnson with the Native Ecosystem Council, appreciates what the beetles create for bugs, birds and other wildlife. She believes the beetle-killed trees cover pockets of two to 10 acres, not forestwide devastation.
“If they’re managing the forest for wildlife, beetle kill is not a problem. All those dead trees are habitat for wildlife,” Johnson said. “It’s natural forest thinning.”
But Gibson said that when a lot of trees in a stand are stressed, whether from drought or competition for limited light and nutrients, the beetles can attack even the healthy trees. What they leave behind are trees unsuitable for logging and fuel for wildfires.
Thinning the forests, whether by hand or with larger commercial equipment, is one of the best tools for ending the epidemic, DiNitto said.
By removing a certain amount of trees per acre ?’ they don’t have to compete so much,” he said.
Others aren’t so sure. Entomologist Scott Black, executive director of the Oregon-based Xerces Society for Invertebrate Conservation, has been reviewing studies of bark beetle containment efforts, and he said the jury is still out on the impacts of thinning.
“It may have some limited, short-term effects, but the studies out there really are contradictory and not very conclusive,” Black said. “Once you get an outbreak, there’s really nothing you can do to control it.”
In addition, the public often equates “thinning” with timber sales, which can bring to mind the clearcuts of years past or new forest roads for huge logging trucks and heavy equipment. Johnson, a former Forest Service biologist, said that when she worked on the Targhee and Gallatin forests in the 1970s and 80s, beetle infestations were used as excuses to clearcut forests.
“When they say everything will die, I think it’s a scam,” Johnson said. “If they’re managing the forests for timber, and are wanting to salvage that wood, then they should just say that. But if they’re managing the forest for wildlife, they should leave the trees there. All those dead trees are habitat.
“I’m in favor of creating fuel breaks for protecting structures. But they don’t have to protect wildlife from wildfires. It’s part of the natural process.”
Gibson and others are quick to note that clearcutting is part of what led to the problem with beetles, because removing all the trees from an area, then planting new trees, means all the trees are of the same age and are vying for the same limited amount of nutrients. That stresses the trees, which can make them vulnerable to infestation.
Instead, many often advocate thinning by smaller cuts using hand tools or through prescribed burns.
“That can improve conditions, especially in an already managed forest,” Black said.
Pesticides can kill beetles, but they only protect a tree for a year or two and often are too expensive to use forestwide.
Scientists have had mixed results with pheromones that mimic the scent put out by beetles, and either attracts them for trapping or sends them away.
“In some places we had success with pheromones from the Doug fir beetles, and are developing one for the mountain pine beetle,” Gibson said. “But with the other bark beetles, we haven’t had those successes.”
“We need a break in the drought before we see a decline in the bark beetle. Eventually, they’ll eat themselves out of house and home ?’ and will either move into adjacent stands or the population will die out if the host is depleted.”
Reporter Eve Byron can be reached at 447-4076 or firstname.lastname@example.org