Beetles that have destroyed millions of acres of trees across North America have defeated nearly every effort to disrupt their deadly march through the forests, but maybe that's just because nobody has been playing the right song.
Researchers at Northern Arizona University in Flagstaff are patenting new technology that may turn beetle against beetle, causing males and females to devour each other instead of mating and killing their host tree.
So far, the technology has worked beautifully in the lab, according to entomologist Richard Hofstetter, so this summer he expects to learn if what works in the lab also works in the forest.
Hofstetter is taking an entirely new approach that is a departure from decades of experiments that have relied on pesticides and other chemicals to end the beetles' reign of terror. He is using sound to disrupt the beetles' lifestyle.
"When we first started we kind of wondered if anything would work," Hofstetter said in a telephone interview. The idea was to find a sound that would make a tree unattractive to the beetles. And they tried just about everything.
Researchers Experimented With Different Noises
Reagan McGuire, a lab technician in NAU's Ecological Restoration Institute, began searching for the "nastiest, most offensive sound," and he came up with the voice of a radio personality he found particularly irritating But it didn't work.
So they tried rock and roll. No joy there either.
But Hofstetter, who has spent a lot of time studying beetle communication, understands how beetles talk to each other. Like most insects, they are influenced by various odors, but they also communicate extensively through noise. The right words, in beetle speak, might mess with their minds.
"It's very dark and smelly" inside a tree, he noted. "So sound is a good way for them to communicate."
Where do you find the right words? By listening to the beetles themselves. The researchers have compiled a large collection of beetle sounds -- males boasting to win the affection of a female, or warning other males to stay away, for example -- and they quickly learned that they could, indeed, talk to the beetles.
Sounds Tricked Beetles Into Thinking Their Partner Is Invader
It worked, but not for long. After a few seconds, beetles ignored the interruption.
"It's kind of like eventually you don't hear the train when it goes through town," Hofstetter said. "You just ignore it."
The researchers think they have worked their way around that problem by introducing frequent changes in the sound, but keeping it close enough to the original that it remains relevant to the beetles. So it's randomized but relevant, Hofstetter said.
In lab experiments, the sounds "tricked beetles into thinking that their partner is an invader," he said. "So they hear these calls that normally would have come from another beetle, and they end up turning on each other, not realizing that it's their mate. They chew on each other, and as a result they don't reproduce."
"We found we could disrupt mating, tunneling and reproduction," he added.
Are Healthy, Noisy Trees in Our Future?
McGuire, watching the action on a computer monitor and listening to the beetles through a headset, said when he played the manipulated sounds he watched "in horror as the male beetle would tear the female apart." At least that's the way it worked in the lab.
It sounds like we could be facing healthy, but very noisy, trees in the future. But the researchers hope to minimize the environmental impact by venturing into the realm of ultrasound. They hope to generate sounds that can be heard by beetles, but not by humans, and still get the job done.
The result that Hofstetter said he hopes to see in the actual forest is living trees, stuffed with beetle carcasses. That may sound a bit extreme, but beetle invasions cause billions of dollars in damages every year.
Last year, 10 million acres were wiped out in Canada's British Columbia. Entire forests have been killed in Alaska, leaving dead timbers that are ripe for fires. The problem has persisted throughout much of the West.
The bark beetles that are attacking pines in many western states are tiny, only about a quarter of an inch long, but they are powerful killers. They eat the tree's living tissue, the phloem, just below the bark, and they can kill a mature tree within a day or two.
Other Approaches to Control Beetles Have Been Mostly Unsuccessful
They also move through a forest so quickly that the invasion can get out of control virtually overnight. If only a few trees are infested, they can be cut down, saving the rest. But in many cases the beetles spread so fast that the entire forest is lost.
Various efforts to control beetles have met with limited success. Beetles can tell by the odor given off by a tree whether that tree is a ripe target. So a few years ago researchers at Simon Fraser University in British Columbia tried to create an odor that would confuse the beetles, making trees that would be good candidates smell unattractive.
Similar approaches have been taken by other researchers, but so far, the beetles have learned to ignore the false odors.
Chemical odors and pesticides have proven disappointing, to some degree. Next summer, Hofstetter and his colleagues will try to succeed where so many others have failed. Billions of trees could use the help.