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 Appetite for Destruction
By Jodi Hausen, Bozeman Daily Chronicle
Bozeman city, Montana State University and state employees are teaming up to fight an infestation of the bark-burrowing beetle that has affected hundreds, maybe thousands, of trees in Bozeman and the surrounding area, Ryon Stover, Bozeman City forester said Tuesday.
Sitting in his office Tuesday morning, Stover had a list of private landowners who he planned to notify about stricken trees on their property. He estimated at least 100 trees in the city proper have been affected - maybe even 200. Crews have found 20 affected trees in city parks, as well as a few boulevard trees.
"And in the surrounding areas, it's big," Stover said.
The MSU campus has also been hit hard. As many as 200 pines there have died and must be cut down. The infestation has affected about 6 percent of all 3,500 trees on the MSU campus.
"Students, faculty, staff and visitors to MSU need to be prepared," said Jon Ford, MSU manager of environmental services. "The effects of this infestation are going to alter how some areas of the campus look. There is no way to sugarcoat this."
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," MSU arborist Rod Walters said. "My whole career has been about trees. I don't like cutting them down, but it's what we have to do if we want any chance of saving the rest."
The city, in conjunction with state entomologist Amy Gannon of the Department of Natural Resources and Conservation and Kevin Wanner, MSU extension entomologist, have recommended that residents in Bozeman fight the infestation on two fronts: try to prevent healthy trees from being attacked in the first place and manage dead and dying trees in such a way as to interrupt the beetles' life cycles and reduce their numbers.
Stover recommended people remove infested trees during the winter when the bugs are in the larval stage and die when exposed to the elements. When live infested trees are cut in warmer temperatures, the flying females simply move to another tree and spread the blight.
"It will be difficult for people to cut down a green tree because it will still be alive, but by next summer it will be orange," Stover said.
Destroying the infested trees and countless beetle larvae nestled under their bark is the most effective way to slow the spread of the infestation, said Wanner, who is also an assistant professor of entomology at MSU.
"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 fireplaces provides opportunity for the larvae to survive, hatch in the spring and spread to a living tree.
"You can't just throw a tarp over it; you need to destroy it," Gannon said.
Disposal of infested trees is tough, Stover said. Because open burns are not permitted in from November through March so private landowners are faced with a dilemma. Infested city trees will be run through a chipper and put in compost heaps at the city landfill.
Stover is working with DNRC Service Forester Curt Tesmer to establish disposal sites for Gallatin, Park and Meagher County residents to drop off infested logs.
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.
Infestations strike western pine forests every 30 to 50 years and 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.
Historically, pine beetle infestations have been confined to native conifer forests. Cities typically escape infestations because of the comparative low density of pine trees and their partial isolation from the forests.
This time, however, it appears the beetles are so abundant 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," Wanner said. "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.
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 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.
Stover said the city is planning on getting Verbenone for their use and to sell to residents. The chemical comes in small packets that are stapled to the trunk of healthy trees about six to 12 inches from the ground on the north side of the tree. To be effective, between two to four packets need to be attached to a tree and, though Stover couldn't say exactly what the price for them will be, they typically run between $6 to $10 per packet, he said. He expects to know more about both the chemical and possible disposal sites next week.
The pheromone-fooling chemical works well both Stover and Gannon said.
"It's not 100 percent effective but it does work," Stover said. He said he recently reviewed a study done in a Colorado city that showed it to be better than 95 percent effective.
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. The sprays are also only a preventative measure to be used on trees that have not yet been infested, Stover said.
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