Slippery Bark Protects Trees From Pine Beetle Infestation: CU-Boulder Study

While it is beneficial for park officials to reduce the number of small trees for fire management, forest officials may want to rethink that strategy in the fight against pine beetle infestation.

It turns out that younger trees are more successful at repelling pine beetles which have trouble getting a grip onto their smooth bark, according to a new study by the University of Colorado at Boulder that was published in Functional Ecology.

Doctoral student Scott Ferrenberg was out walking through a stand of high-elevation limber pines with Jeffry Mitton, a professor of ecology and evolutionary biology, when they noticed that the signs of pine beetle infestation were common only on patches of rough 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 said. “We thought the beetles were either choosing to avoid the smooth surface, or they just couldn’t hang onto it.”

Listen to Ferrenberg discus the findings (Story continues below):

To test their hypothesis, Ferrenberg and Mitton put 22 pine beetles on a rough patch of bark, where all but one beetle hung onto the surface. When they placed the beetles on a smooth patch of bark however, all of the beetles fell off in less than one minute.

Their conclusion correlates with another study by Ferrenberg, Mitton and Jeffrey Kane of Humboldt State University in California published in Oecologia, which found that trees with more resin ducts -- typically young trees -- are also able to better resist the pine beetle. Resin ducts are a defense mechanism of the tree that can help it pitch out the beetles, which bore into the bark.

According to the Rocky Mountain National Park Service, there is currently "no effective means of controlling a large beetle outbreak," and once one tree is infested, it's nearly impossible to save that tree.

While the younger trees may be better suited to combat the pine beetle however, they are also more vulnerable to prescribed burns.

“This contradicts the approach that has been historically common for fire management,” Ferrenberg said. “The common approach for fire is to cut all the small trees. But if you want to defend a small amount of land against bark beetles, that may not be the best strategy.”

Watch Ferrenberg discuss the pine beetle infestation issue below in a video from CU-Boulder:



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