Insect research adds fuel to wildfire prevention |

Insect research adds fuel to wildfire prevention

Merry Thomas

USDA Forest Service. Mountain pine beetles are one of many bark beetles found in the Lake Tahoe Basin.

University of Nevada biochemists’ recent discovery of a key gene in bark beetles could eventually help firefighters in wildfire prevention.

The discovery would eradicate the hundreds of species of bark beetles that decimate western forests, particularly during droughts.

“The forest system has been slightly out of whack since the Comstock logging,” said Dave Fournier, vegetation planner for the U.S. Forest Service and vegetation administrator for Pathway 2007. “Forests are uniformly dense in the Sierra Nevada.”

Local scientists cited the wildfires that ravaged Southern California in the fall of 2003 as a result of weakened trees plagued with bark beetles.

Anna Gilg, a post-doctoral fellow at UNR in biochemistry and molecular biology, was lead author of an article published last month in the journal Proceedings of the National Academy of Sciences.

She worked alongside a team of about a dozen UNR biochemists that included two professors and graduate students. Jeremy Bearfield, Claus Tittiger and William Welch co-authored the article with Gilg titled, “Isolation and functional expression of an animal geranyl diphosphate synthase and its role in bark beetle pheromone biosynthesis.”

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The size of a grain of rice, one bark beetle alone has little effect and can be eradicated by application of the pheromone oleoresin, according to Gary Blomquist Ph.D., head of the lab. But when a mass attack occurs, a forest loses many trees.

Gilg’s discovery ended a decade-long debate among scientists about the pheromone. It revealed that the insects produce a pheromone from their own bodies. This is significant because now molecular biochemists can work on finding a way to interfere with the pheromone production and therefore cut down on the beetle population.

“The pheromone attracts other beetles, signaling that a tree is suitable as a host, and it becomes prey to a mass attack,” Fournier said.

The pheromone is a perfume that’s exuded to attract mates and therefore maintain the many species of the insect family Scolytidae, each of which is particular to each type of pine tree.

“What happens is, they chew through a tree and then poop out the pheromone that attracts males and females,” Blomquist said.

The beetles are difficult to control because they live underneath bark most of their lives, from the egg stage to adults, leaving only for a few hours to fly to another tree.

Forest managers identify pine trees that are infested by bark beetles by the appearance of their pitch. Instead of having a milky-white color, those attacked by beetles have a reddish or yellow color, Fournier said.

The most recent local bark beetle attack occurred in the mid-1990s and resulted in a loss of 20 to 30 trees per acre in the hardest hit areas, according to Fournier.

“The area around Spooner Lake was severely hit,” he said.

Historically, an average annual loss of trees is about eight to 10 per acre, he added.

The drought of 1986 to 1994 weakened many trees, particularly Jeffrey Pines in the Tahoe Basin, making them vulnerable to the area’s three main species of bark beetle, Fournier said.

Currently the Tahoe Basin forest is healthier because of the long, wet winter of 2004-2005, Blomquist said. Still, he advises people to safeguard landscape pines against beetles by watering them.

Both Rex Norman, public affairs officer for the U.S. Forest Service, Lake Tahoe Basin Management Unit and Fournier concur that another use of the pheromone might be to harvest it to trap bark beetles.

In recent years, the forest service and fire districts have been working to thin the dense forest growth by controlled burns and by cutting down some trees. The efforts serve to prevent wildfires as well as discourage beetle infestation.

“If we can ID an area (of beetle infestation) we can reduce the amount of density and it benefits the healthy trees and the possibility of insect spread,” Norman said. “There’s not a lot you can do with chemical treatments.”

Bark beetles have plagued forests throughout the West, prompting British Columbia to organize a Mountain Pine Beetle Task Force, and many western states to revise their forest management techniques.

“Bark beetles are the most destructive insects in the coniferous forests of the Southwest,” Arizona scientists said on an education Web site.

University of California, Davis scientists put it into perspective: “Beetles can contribute to the decline and eventual death of trees, but with a few exceptions, they usually are not the initial cause.”

Dead trees are a natural part of a forest and can be caused by many things, from beetles to weather, lack of moisture or root rot,” Norman said.