A new study from researchers at the University of Colorado, Boulder shows that younger trees with smoother bark are better at repelling the mountain pine beetle.
The epidemic pine beetle attack has spread across western states since 1996, affecting millions of acres of forest, including those in the Greater Yellowstone Ecosystem.
Colorado doctoral student Scott Ferrenberg, who led the study, noted that the mountain pine beetle had a harder time holding on to smooth-bark trees, which have a slippery surface. These tend to be the younger trees in a stand. The findings, published in the journal Functional Ecology, may help land managers decide which trees to cull and which trees can help protect forested areas against the pine beetle.
To test their findings, the researchers placed 22 beetles on a rough patch of bark, then on a smooth patch. After five minutes, 22 beetles held onto the rough bark, but all the beetles had fallen off the smooth bark.
"We found trees that had both textures on the same stem, and when the tree was attacked, it was on the rough surfaces," Ferrenberg says. "We thought the beetles were either choosing to avoid the smooth surface, or they just couldn't hang onto it."
The results — especially when combined with the findings of a second study also recently published by the research team — provide information that may be useful to land managers who are trying to keep public parks and other relatively small forested areas healthy.
The research suggests that when culling properties to resist the mountain pine beetle, land managers should consider cutting down older trees. Fire management usually suggests cutting the small trees, but this may not be the best strategy for defending against the beetle.