Massive Infestation of Beetles Threatens Mountain Pines in Western U.S.

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A major infestation of the mountain pine beetle, a scourge stretching from New Mexico, in the U.S., to British Columbia, Canada, has been turning vast areas of formerly green pine forests to rust red, and slowly killing them.

The beetle infestation has been growing “exponentially” since 2006-07, according to the Forest Service management team in Laramie, Wyoming, and has so far claimed millions of acres of pine forest in Montana, Colorado, and Wyoming. North of the border, British Columbia has already lost over 33 million acres of lodgepole pine forest due to the ravages of this type of bark beetle. And more recently (in 2008), Alberta province is come under threat due to an aberrant wind storm that apparently lofted the beetles across the continental divide.

The black, hard-shelled beetle, a member of the genus Dendoctonus (which mean “tree-killer” in Latin) drills a hole through the tree’s bark and lays its eggs in a tiny “room” that it makes in the tree’s softer and more nutritious cambium (the dual-layer of xylum and phloem tissue just beneath the bark that provides nutrients to the tree). As the larvae hatch, they fed off of the sweet-tasting cambium, and also inject a symbiotic fungus into the cambium that blocks the movement of pine sap that would normally swallow up the larvae. This fungus secrets a protein that stains the cambium blue.

The pine trees are not without some defense here–they respond by secreting a whitish resin to fill up the beetle’s drill holes–but these defenses can be neutralized by either of two factors: the insect’s response (releasing a pheromone that signals other beetles to swarm the site of the resin defense), and/or, drought (which hampers the ability of the trees to make resin, needing water to do so).

Insecticides help some, but only when they are sprayed, bottom to top, on trees that are no more than 4 inches around (the trees become most vulnerable to attack when they reach about 5 inches in circumference). This leaves older, larger trees most at risk.

A stand of trees that is very far in the beetle infection cycle (loc.- north of Breckenridge, CO, looking east.

Many ecologists have warned and predicted (for several years now) that changing weather patterns (such as less rainfall, and more sunlight, in some regions) will result in ecosystem imbalances, and that these imbalances would lead to various parasitic and insect infestations. With the mountain pine beetle infestation–which is believed to be the largest insect infestation in the (known) history of North America–their warnings and predictions have become reality.

The infestation is disrupting other ecosystems as well, such as in Yellowstone Park, where the white bark pine is under attack, These pines produce pine nuts favored by black bears prior to their hibernation. Dead tree also do not retain snow in their branches, thus allowing too much snow to pile up in streams which impacts fish spawning in the Spring. On the other hand, insect-eating birds should thrive. However, in general, the infestation will result in a major habitat loss for hundreds of species of animals.

Vast areas of dead pines also pose a major wildfire risk–a risk that grows more severe after the dead trees have fallen and remain on the forest floor for 4 to 5 years.

Industry is also being hurt. The timber industry is having to increase bleaching of the wood (to remove the blue fungus stain) for paper making. But even more so, the tourism industry (as in Colorado and Wyoming) is being hurt, and may dwindle over the next few years to nothing as the once scenic, lushly forested landscape turns rust red and dies.

At present, the infestation threatens to continue its spread Eastward, and may reach the Great Lakes region sometime this year, or next.

second photo (mountains) credit: Hustvedt, CC – Attribution – Share Alike