Bark beetles have been unstoppable across the West, destroying 33 million acres of forest in British Columbia and millions more in the United States, and the only thing that’s slowed them has been running out of trees to devour. But taking a page from the U.S. troops who tried to drive Manuel Noriega into surrender by playing loud music, researchers at Northern Arizona University have developed acoustic assaults that deter the beetles and can drive them away from the trees.

Not to put too fine a point on it, but this could be huge, the first real solution to the beetles’ massive environmental devastation.

The scientists’ investigation began when they sliced dead trees into layers and brought beetle-infected wood into the NAU lab, creating what they call “ant farms” sandwiched in Plexiglas, and then they blasted the beetles with metal and Rush Limbaugh commentary played backwards. But “after a few minutes they ignored it,” said Richard Hofstetter of NAU’s School of Forestry. “They seem to habituate to the sound.”

So then Hofstetter and his team recorded the noises the beetles themselves make, tweaked them, and piped them back into the ant farms. The results were nearly instantaneous.

“We could use a particular aggression call that would make the beetles move away from the sound as if they were avoiding another beetle. Or we could make our beetle sounds louder and stronger than that of a male beetle calling to a female, which would make the female beetle reject the male and go toward our speaker. We found we could disrupt mating, tunneling, and reproduction. We could even make the beetles turn on each other, which normally they would not do.”

The NAU scientists have developed a device that would be drilled into the outer layer of the lodgepole pines and other trees that beetles favor, pumping the sound waves under bark. Costing about $100 a tree, it’s cheaper, less environmentally disruptive, and far more effective than other methods.

“It would create a virtual wall,” said Hofstetter, “and protect high value trees. People now spend hundreds to protect a single tree.”

Red shows Colorado 2008 damage alone.

A wall might be exactly what’s needed. Although B.C. authorities say the beetle epidemic is over in the province because there are no more living trees for the beetles to infest, they’re worried the tiny insects will migrate east into the boreal forest of eastern Canada, one of the largest carbon sinks on the continent. Why is that a problem? Dead trees don’t absorb carbon. They also burn, releasing carbon into the atmosphere even faster. In B.C., estimating the years 2000 to 2020, a study in Nature found the beetle impact “converted the forest from a small net carbon sink to a large net carbon source both during and immediately after the outbreak. In the worst year, the impacts resulting from the beetle outbreak in British Columbia were equivalent to 75% of the average annual direct forest fire emissions from all of Canada during 1959–1999.”

Beetles are adapting to new species of tree, too. And while the boreal of eastern Canada is a long way from B.C., those bugs can travel. A freak wind storm in 2006 blew beetles into northern Alberta, where they’d never been seen.

So, Metallica is ineffective, and Rush doesn’t rile. So which of the most abrasive beetles tunes to play? The researchers are still figuring out what sounds lead to what behaviors—and how the beetles even hear. “Our primary goal is to prevent invasion, to get them to sense the sounds and then exit. Once they’re in the tree we can target other behaviors—they turn on their mate and start to chew them,” Hofstetter said. “We actually have no idea how they hear, if it’s on the head or the feet.”

Hofstetter anticipates the anti-beetle boombox should be ready for market by 2011. “It’s about a year away,” he said, “maybe sooner. It all depends on funding, which we don’t have.”

Breakthrough: Bark Beetle Epidemic Could be Staunched by Anti-Beetle Boombox

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