Beetles, disease on march through forests
Mon., Nov. 1, 2004
Inland Northwest evergreens are turning red and dying because of a growing infestation of beetles and tiny caterpillars.
Cycles of insect outbreaks have occurred for thousands of years, but some scientists believe decades of fire suppression have set the stage for infestations never before seen in modern times. And in the region’s high country, a combined beetle and disease problem is threatening to wipe out a pine species that serves as the food foundation for a fragile ecosystem.
The most visible sign of insect infestation can be spotted on the mountainsides north of Interstate 90 near Lookout Pass. Large patches of red, dead pine forest are evidence of the mountain pine beetle outbreak. Last year, the tiny beetles chewed through 1,500 acres of mature lodgepole pine on the Idaho side of the pass and even more across the border in Montana.
The beetles also destroyed 19,000 acres of forest north of Bonners Ferry, Idaho, last year, said Ladd Livingston, an entomologist with the state’s Department of Lands. Results from the 2004 annual aerial survey of infestation have not been completed.
“All I can say is they’re bigger,” Livingston said.
At the same time, Western spruce budworm numbers are surging in Idaho’s forests. The caterpillars infested 22,000 acres two years ago. Last year, the numbers jumped to 125,000 acres, including patches near Priest Lake and along the North Fork of the Coeur d’Alene River.
The budworm typically eats the needles of fir and spruce, but the pest also is attacking hemlock – something not seen since the 1920s, said Carol Randall, regional entomologist with the U.S. Forest Service. “We’re really not sure what to make of it,” she said.
Although the evergreens may look brown and dead, the trees are sometimes able to survive a budworm attack, Randall said. In fact, researchers now believe budworms help fertilize the forest with ammonia and have noticed a surge in the growth rates of infested trees in the years following an attack.
Foresters say the greatest problem is the dying whitebark pine trees in high-elevation forests. Blister rust, an exotic pest that has already wiped out much of the Inland Northwest’s white pine trees at lower elevations, is now attacking whitebark pine. The trees are being doubly punched with a mountain pine beetle infestation.
“It’s really frightening,” Randall said. “We’re really worried about the ability of that species to cope.”
The loss of whitebark pine could cause a catastrophe for wildlife, said Sandy Kegley, regional entomologist with the Forest Service. Whitebark pine is one of the few trees capable of growing at high elevations and its cones supply a critical food source for birds, squirrels and bears. The Forest Service has been collecting seeds from the few trees that appear to be unaffected by the blister rust. Offspring are being grown at the agency’s nursery in Coeur d’Alene.
The trees are in “rapid decline” across the West, Kegley said, including in the Selkirk Mountains of North Idaho. About 40 grizzly bears are believed to roam the area and the pine nuts are a critical food source.
“It’s hard to make those predictions, but it doesn’t look very good up there,” Kegley said. “I see more red trees every year.”
Foresters believe the ongoing battle against wildfire is one reason behind the growing insect and disease outbreaks. Until the 1930s, an average of 31,000 acres of forest burned each year in North Idaho, according to Forest Service analysis of tree growth rings. For the past three decades, fire has only burned about 660 acres per year.
Fire acts as an important renewal agent for forests, said Art Partridge, a retired forestry professor at the University of Idaho. “These diseases and insects are there for a very good purpose. They take out the old stuff and bring in the new,” Partridge said.
The last major fires in North Idaho were in 1910. Lodgepole pine born from those fires are the prime age for a mountain pine beetle attack, Partridge said. The beetles typically avoid trees less than 80 years old.
Control efforts are rarely effective, Partridge said. “Once it’s started, we’ve never been able to control it. I’ve not found a case yet where control has been achieved.”
Other foresters disagree and say cutting infested timber helps contain the outbreak. In British Columbia, a massive outbreak of mountain pine beetle has wiped out more than 10 million acres of trees since 1993. The outbreak is not expected to peak until 2008, when more than 80 percent of the province’s mature pine has been destroyed, according to information from the British Columbia Ministry of Forests.
The problem is too large to be halted, but Idaho’s infestation is small enough to manage, said Allan Carroll, a research scientist with the Canadian Forest Service.
“When you have an outbreak the size we do, there is virtually nothing you can do from the standpoint of controlling it, but what you can do is work at the periphery and slow its spread,” Carroll said. “The only way to achieve a management goal is to get on these populations early. You need to detect it and jump on it, just like you do a fire.”
Although beetles are chewing through the trees, Carroll emphasized that the true problem was a lack of wildfire and increasing global warming. Beetles are a native species. Until recently, cold winters and a diversity of tree species and ages helped keep their populations in check, Carroll said.
“We put the fires out and let the lodgepole grow. This is why we have as much mountain pine beetle as we do,” he said. “The solution, of course, is to begin to manage the land base in such a way to emulate various age class structures of pine – break it up, ensure we don’t have as much contiguous area of mature pine.”
The U.S. Forest Service has proposed a 225-acre salvage logging operation for Lookout Pass, but a final decision on the project won’t be made until mid-November. The agency is also working to protect valuable stands of pine at the Look-out Pass Ski Area with chemical decoys. The devices emit the same pheromone used by resident mountain pine beetles to indicate their host tree is already infested.
Using the chemical traps is not cheap – 20 are needed to protect an acre of trees and each trap costs $6, according to the Forest Service.
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