Pine Beetles ATTACK!

Wednesday, April 29, 2009

By Brigid Mander

Jackson Hole, Wyo.-Across the Rocky Mountain West, islands of green pine trees dot the landscape, isolated from one another by a sea of dying, and dead, rusty colored pines. 

A decade of elevated onslaught by the tiny dendroctonus ponderosa, or mountain pine beetle, has wrought havoc on pine forests from New Mexico to British Columbia, and the latest beetle epidemic is well on its way to turning green Teton hillsides to wildfire fuel.

Large-scale destruction can be seen on Togwotee Pass, in Granite Canyon, down the Snake River Canyon, in the forests around Pinedale, and in the Kemmerer Forest District, among other places, according to Liz Davy, silviculturalist and timber program manager for the Bridger-Teton National Forest.

Susceptible pines in local forests include lodge pole, white bark and limber pines.   
Millions of acres of trees in the US and Canada have been killed in what is seen by foresters as elevated levels of a normal forest cycle. The effects of the pine beetle in Teton County itself are not as disturbing as other parts of Wyoming, such as the decimation seen in the Medicine Bow and Routt National Forest in southern and central Wyoming.

This distinction is due in part to the relative diversity of the local forests as well as to the simple, unfortunate fact that the beetles haven’t yet taken all the food sources in the area.  But they will – there is no question.  
“We are very concerned.  We are in an epidemic of Mountain Pine Beetle,” says Davy.

More beetles, Weaker trees
Female beetles, about the size of a grain of rice, bore into susceptible trees and send out a pheromone to attract male beetles to the food source. The beetles feed on the phloem, which brings nutrients from the root to the crown, overwhelming the tree’s defenses and effectively starving the tree in a matter of weeks. Trees will increase their resin production to fight off beetles, but even in the healthiest trees, it is not a guaranteed defense, and most trees succumb in short order. Beetles lay their larvae under the bark of the tree, beginning another generation of beetles, whose lifespan is about one year.

Exceptionally high levels of beetles have been seen all through the Rocky Mountain West, and are expected to kill virtually every mature lodge pole pine in their path.  The increase in recent years has been blamed on everything from climate change to fire suppression tactics, but it is more likely a convergence of factors that favor the beetles and weaken the pine forests. 
Beetle larvae have a temperature dependent mortality, and in the past populations have been kept in check by prolonged cold temperatures killing off the larvae.  Prolonged droughts in the region have left trees stressed and less defensible, as well as more attractive to beetles, who can actually pinpoint stressed trees as easier targets.  But some forestry experts see an opportunity to promote different strategies for managing public lands. 

Years of fire suppression tactics and logging restrictions in some areas have left pine stands densely packed once trees reach maturity, and trees must compete for nutrition in very tight quarters.  In addition to contributing to tree stress levels, this crowding happens just as trees reach about 80 years, or eight inches in diameter-putting them into the beetles favorite food category. 

Human intervention
Protective measures developed by Forest Service researchers include thinning of overcrowded stands of pines. However, trees are slow to respond to any environmental stimulus, whether the end of a drought or thinning, and require anywhere from three to five years before they return to a healthy, non-stressed state.  

Other measures include hanging packets from trees that emit a pheromone, verbenone, that communicates to the beetles that certain trees are not good targets or are already fully occupied. An insecticide called Carbaryl is also sometimes used by the Forest Service to repel beetles, and is highly effective when sprayed heavily before beetles attack. 

As far as the Forest Service is concerned, these methods are useful around their buildings and amenities like campgrounds, where green trees matter for tourism, but beyond small areas, they are cost-ineffective and not beneficial for long-term forest health.   

Large-scale application of any of these methods is too labor intensive for feasible application by the Forest Service, says Davy. Researchers are looking for ways to apply the pheromone verbenone over large areas. Some promising California-based research has suggested that applying verbenone flakes from the air could be a way to protect larger stands of high-value pines, such as those around ski areas or in neighborhoods that may rather coat their trees in pesticides than lose them. 

Evidence does show that when beetle populations are high, however, it is difficult to deter them even with the use of pheromones, according to Jeff Witcosky, an entomologist with the Rocky Mountain regional Forest Service office.

As far as thinning trees in the forest, Bridger-Teton National Forest’s Davy is among the many scientists who have seen public opposition first hand.  Thinning must be done several years before beetle attacks, and public resistance to these tactics when they do not see an imminent threat tends to be very strong. And once the beetles have arrived, it is too late for the trees, which still need several years to respond positively to decreased competition. 

It’s difficult to convince landowners and the public when they don’t see a need, Davy said. By the time people see damage and start asking for help, it is too late to do anything.

Ultimately, forestry experts contend that it is a natural cycle, which they can’t do much to prevent in wilderness areas. Even if a large scale, low cost and effective remedy existed, they wouldn’t advise much interference in the cycle. And in any case, right now, everyone agrees that whatever the causes, the epidemic is too big to manage, except to save small selected tree stands in high value areas.

Spraying locally
Like the Forest Service, homeowners must contend with the beetle problem on a yearly basis, or risk losing their mature pines. This has resulted in tree services that are well versed in effective beetle control on a small scale.

Local tree services in Teton County have their work cut out for them in protecting pines on private property from becoming more beetle kill.  Most advertise beetle mitigation, through either pheromones or spraying, and thinning to promote healthy densities and keep trees stress-free.

There has been an increased demand for beetle mitigation for almost a decade, according to Travis Eva, of Jackson-based Trees-R-Us, a tree care company.  “We get a lot of beetles, but mountain pine is the most prevalent,” Eva said. “We do a lot of work for private homeowners, even if they only own an acre, that hold plenty of ripe pines for beetles.” 

Hiring researchers and pooling resources with others battling the problem in places like Colorado and Idaho, Trees-R-Us follows the latest developments in beetle defense, but after all the research, it seems like the most surefire defense for individual trees is spraying.  Employing the insecticide Astro over the also highly effective Carbaryl, Eva says they have had good results in protecting pine assets on private property. 

Beetle-kill can be seen in most areas, but down on Fall Creek Road the effects of neighbors being able to hire services en masse can be seen clearly.  In the vicinity of Crescent H, beetle attacks have been held at bay relatively well, whereas elsewhere on the road larger stands of dead trees dot the landscape where there are not as many houses watching closely over the pine stands.

To keep the bugs away, mature pines must be sprayed heavily and before beetle infestation on an annual basis, and very thoroughly.  “If you miss any part of the tree, the beetles will attack that part, says Eva.  “I don’t think I would even say people are nervous about the beetles anymore.  At this point I think homeowners are just tired of it.” 

Although it may be costly to protect trees from beetles, leaving them to die isn’t cheap either, as removing dead trees before they become fire hazards can run up a hefty bill as well.  And unlike in the wilderness, where fires can be allowed to run through and clean out dead things, in a neighborhood not everything can be left to nature. 

Forest cycles and civilizations
When people choose to live close to wild landscapes, a changing landscape is part of the deal, and locals should be at least a little relieved that the diversity of tree species in northwestern Wyoming is much greater than in other areas, that have lost all of their mature vegetation to the beetles.

“Green, red, black, green – those are the colors of a lodge pole pine forest,” says the Caribou-Targhee National Forest’s Tom Silvey, in a lighthearted, but bluntly accurate, description of forest cycles. 

Green for living forest, and red and black for beetle-kill and fire charred acreage.  The Caribou-Targhee Forest that Silvey helps oversee suffered a major pine beetle infestation in the 1960’s and 1970’s, when more than 100,000 acres were lost from 1.1 million forested acres.  Although they are seeing some infestations on mature pines in their southern lands, the C-T forest is mostly sitting this one out and overseeing the regeneration of a healthy lodge pole pine forest.

The areas of the C-T forest that were affected decades ago are currently populated by trees that are far too young for beetle tastes, and thus are being bypassed by this epidemic.  The Yellowstone fires spanning the 1970’s and 1980’s, including the famed conflagration in 1988 that left 980,000 acres (including many that were already dead from beetles) burnt in the park and seven hundred thousand adjacent to the park have also resulted in a regenerating pine forest that is well below the age of attack. 

Raging natural wildfires, however, even if they may be the way forests have evolved to cleanse and regenerate, are clearly not always a feasible solution.  Near populated areas, the consensus is that the best methods for dealing with the infestation is are to keep trees healthy, and mitigate with the pheromones or chemicals if the trees are valuable enough to whoever is taking care of the land-homeowners, ski resorts or the government. 

Beyond that, the USFS will continue to research the role of beetles in a healthy ecosystem and forestry experts will hopefully glean useful information.  Homeowners and tourists will lament the eyesores amongst sweeping pine vistas, but for most mature pines right now across the North American West, well, their time has come. 

Despite all the concerns, the Caribou-Targhee’s Silvey said, “It’s the history of a lodge pole pine forest.  It’s just sort of a boom and bust cycle.”  PJH


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