Released December 1, 2008
BOZEMAN, Mont. - As many as 200 pines at Montana State University have died and must be cut down due to an infestation of mountain pine beetles, which are killing trees on campus, in surrounding communities, and many of the pine forests of the western U.S.
"Students, faculty, staff and visitors to MSU need to be prepared. The effects of this infestation are going to alter how some areas of the campus look," said Jon Ford, MSU manager of environmental services. "There is no way to sugarcoat this."
The infestation has affected approximately 6 percent of all 3,500 trees on the MSU campus. Most of the infested trees are on the campus margins, however some of the infested trees are spectacular, old pines in very visible places on campus and will be cut down.
"Basically, they are already dead. They look green now, but by next spring they will be rust red," said MSU Arborist Rod Walters.
"My whole career has been about trees," Walters said. "I don't like cutting them down, but it's what we have to do if we want any chance of saving the rest."
MSU will cut infested trees through the winter.
Infestations strike western pine forests every 30-50 years. Scientists suspect the unprecedented scale and intensity of the current infestation have been influenced by the preponderance of over-mature trees, lack of very cold winter temperatures in recent years, and nearly a decade of drought.
MSU Facilities Services groundskeepers first noticed a few infested trees this spring.
Historically, pine beetle infestations have been confined to native conifer forests. Cities have typically escaped infestations because of the comparative low density of pine trees and their partial isolation from the forests.
This time, it appears there are so many beetles that the flying females have overflowed or been blown into the cities. There have been limited infestations in Bozeman before, and based on this prior experience, arborists and scientists did not anticipate the extreme extent to which the urban forest would be affected in this invasion.
"This is the most serious infestation anyone has seen in 100 years," said Kevin Wanner, MSU Extension entomologist. "Additionally, this is the first time anyone has seen urban forests infested to this degree."
Entomologists and arborists are not optimistic about the short term future of Bozeman's pines. The city may experience widespread destruction of its urban pine forest in the next few years, and it will likely take that long for the infestation to die out. Afterwards, replanting of pines could be safely undertaken.
MSU is not alone in being struck. Pine beetle damage has spread across Bozeman, in the surrounding forests and throughout the West. Pine beetles showed up in British Columbia in 2002 and more than 9 million acres of forest have been substantially damaged to date. An estimated 3.9 million acres have been infested in Colorado, Montana, Wyoming, Oregon, Idaho, Utah and Washington.
Female mountain pine beetles bore into a tree's vital inner bark - its circulatory system - and then tunnel vertically. Healthy trees excrete sap to fight off the attack. That sap appears on the tree's trunk as popcorn-shaped nodules called pitch tubes. The pitch tubes can vary in color with the tree species. Infested Scotch pines, with their yellow sap, are among the easiest to spot. Pitch tubes are the easiest way to identify an infested tree.
After the females bore their tunnels, called galleries, they emit a pheromone to attract males for mating. This pheromone also attracts other females, causing a mass attack. Upon entry into the bark, the female introduces a fungus that impairs the tree's circulatory system. This reduces the tree's ability to repel the attack and provides additional food for the future brood of larvae. After mating, females lay eggs that hatch into larvae in a few weeks.
The larvae feed on the host tree as temperatures warm the next spring. They tunnel mostly horizontal galleries from the vertical egg chambers and eventually girdle the tree, killing it. After feeding the larva emerge as adults to find new trees to infest. Emergence typically occurs around June 15 and again in late August.
The City of Bozeman Forestry Division, in conjunction with State Entomologist Amy Gannon of the Department of Natural Resources and Conservation (DNRC) and Wanner, who is also an assistant professor of entomology at MSU, have recommended that residents in Bozeman fight the infestation on two fronts: trying to prevent healthy trees from being attacked in the first place, and managing dead and dying trees in such a way as to interrupt the beetles' life cycle and reduce their numbers.
Destroying the infested trees and countless beetle larvae nestled under their bark is the most effective way to slow the spread of the infestation, Wanner said.
"By cutting down the trees, we disrupt the beetles' life cycle so the next generation can't emerge and do more damage," he said.
After cutting, infested trees must be burned, buried, have the bark removed, or chipped to ensure the destruction of the larvae. Storing infested wood for wood stoves or other uses will not stop the beetles' life cycle.
"You can't just throw a tarp over it; you need to destroy it," Gannon said.
City of Bozeman Forester Ryon Stover, and DNRC Service Forester Curt Tesmer are looking into the possibility of a disposal yard where Bozeman residents can drop off infested logs. MSU will be working closely with the city to coordinate beetle-kill management efforts and final disposal of dead trees.
Next spring, MSU also plans to use Verbenone, which mimics a pheromone released by female beetles when an infested tree is full. Other beetles sense this chemical message and might bypass a tree they would normally attack, reacting as if the tree is already full of beetles and go looking for a less infested victim elsewhere.
"By using Verbenone, we can sometimes trick the beetles into thinking a tree is already infested," said Gannon.
Verbenone comes in small packets that are stapled to the trunk of healthy trees.
"Verbenone can be fairly effective in low populations," Gannon said. "In residential areas, it's best to apply two to four pouches per tree. Be sure to follow all label instructions."
Verbenone can be ordered directly from the two companies that manufacture it: Pherotech (1-800-662-8447) or http://www.pherotech.com and Synergy Semiochemicals Corp., (604-454-1121) or http://www.semiochemical.com. Gannon said both companies have excellent Web sites with detailed information.
There are several insecticides that can be applied as a spray, but MSU officials have chosen not to use them because they are only partially effective, are toxic to humans and honeybees, and are hard to keep from drifting off the target tree.
For further information, MSU has created a Website, http://www.montana.edu/pinebeetle describing its management plan in detail and offering a clearinghouse of information on the mountain pine beetle for area residents.
--30--
http://www.montana.edu/cpa/news/nwview.php?article=6595
Contact: Jon Ford, (406) 994-5459, jford@montana.edu
