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Battling the Bark Beetle - 2002-11-10

Thousands of hectares of forest burned across the American West this past summer. Many of those same forests are once again under attack, not by fire, but by tiny beetles, no bigger than a pencil lead. Throughout Northern Arizona, especially around Prescott, the beetles have killed thousands of trees, leaving the forests mottled with brown, dead patches. Entomologists say there's no immediate end to this beetle onslaught.

On a hillside of green pine trees, Tom DeGomez stands under a ponderosa pine covered with rusty brown needles and sinks a small hatchet into the pockmarked bark.

Mr. Degomez is the Coconino County extension agent and he's been getting a lot of calls about trees like this one. So, today, he's searching for the culprits - tiny beetles. And he doesn't have to look very long.

"Here's a little bark beetle here," he points out. "You can see he's about the size of a grain of rice, he's brown, about as big around as a pencil lead."

These tiny beetles are killing off pines in record numbers. In normal years, a few rust-colored trees would go unnoticed, but this year isn't normal. Even with recent soaking rains, Arizona is still in a drought and its forests are over-crowded perfect habitat for bark beetles.

According to U.S. Forest Service entomologist Kurt Allen, trees in Arizona aren't the only ones under a attack. "We're seeing outbreaks we haven't seen in 50, 100-200 years, they're all across the west and the same thing is happening in Utah, Idaho, Montana," he explains.

... Not to mention Alaska, Colorado, South Dakota , New Mexico, Nebraska and even Kansas. Mr. Allen notes the outbreak is so enormous, he's convinced the bark beetles could kill the West's forests, if wildfires don't get them first. "There's whole hillsides, mountain valleys that are 70 to 80 percent dead, just gray and red. There's not much green forest left in some places," he said.

Trees have a built in defense against beetles pitch. Once a beetle drills into the bark, this yellow goo forces the creature out in a year with normal rainfall, that is. Coconino National Forest spokesman, Ken Fredrick looks at several tiny holes in the bark of one infested tree.

"The tree has attempted to pitch out the beetles that have bored into the trunk," he says. "But because this tree didn't have enough moisture, it wasn't able to muster its defenses against a beetle attack."

Now there are so many beetles you can hear them tunneling through the bark. Although they're quiet today, Mr. Fredrick says they you can sometimes hear them.

So how do hundreds of beetles decide to bore into a single tree? Pheromones. This natural perfume given off by a few colonizing beetles signals others to join. When the food is gone, the beetles send a different scent to deter future visitors. And it's this smell that may be the most promising weapon in the arsenal of scientists trying to stop the beetles.

Joe McMillan, a bark beetle specialist in Flagstaff, Arizona, has been working with a group to create beetle traps that use pheromones as bait. "We haven't figured out the best method of trying to trap out all the beetles in a given area in these traps and we need to be able to catch enough to reduce the population," he explains.

Mr. McMillan says the traps could work on a small patch of woods, but they are too expensive for a large scale operation. He adds that stopping the beetles may come down to a change in forest management and the weather. "We need forest management to bring the population down in size," he says. If there's a severe cold snap the beetles could die out. And if we get above average precipitation that could kill them off."

So, while entomologists wait for a really snowy winter or a major forest thinning project, they continue their search for a winning strategy in the battle against the bark beetles.