Vast swaths of reddish- brown pines dominate the landscape on the trails of Yellowstone National Park in Wyoming and down ski runs around Aspen, Colorado. The morbid color, by now a staple of the Rockies, comes not from fire or some exotic disease but from an insect no larger than a grain of rice—the bark beetle.
North American foresters have tracked the invasive bark beetle for centuries, but in the last 15 years its numbers have exploded. Beetles are now wiping out trees, even whole forests, at an unprecedented pace; they ravaged 9.2 million acres of forest in the western United States in 2010, according to the Forest Service, three times as much as that destroyed by fire. In British Columbia, the devastation over the last decade covers an area larger than Florida.
Until recently there was virtually nothing landowners could do to protect even small parcels of forest from bark beetles. But after a half century of detective work, a small group of scientists has come up with a novel and surprisingly effective means of defense: hijacking the beetles’ sense of smell.
Like ants and honeybees, beetles communicate via scented chemicals called pheromones, one of which warns the insects to stay away from particular trees. Now researchers are dispersing this pheromone, called verbenone, placing a molecular shield over thousands of acres of hardy green pines in western ski resorts, nature reserves, and campgrounds. “Verbenone is just fantastic,” says David Wood, a retired forest entomologist at the University of California, Berkeley. “It’s the only effective treatment, period.”
