Down To Earth

Feb 4, 2011 7:26 AM by Bea Karnes

Frigid weather likely won't ice bark beetles

GRAND JUNCTION (AP)-Anyone hoping that sub-zero temperatures have put Colorado's pine beetle infestation on ice is likely to be disappointed: federal officials say it would take about a week of frigid weather to kill the bugs.

The beetles become hardier during winter, Bob Cain, a U.S. Forest Service entomologist told The Daily Sentinel in Grand Junction.

"This (cold) snap in midwinter is well within the normal range for what the beetles would have evolved with in the Rocky Mountains," Cain said.

A factor in the spread of the tree-killing bugs has been the lack of sustained frigid weather. The bark-beetle epidemic that started more than a decade ago has wiped out 4 million acres of pine trees in Colorado and southern Wyoming.

The bugs that burrow under the bark are more vulnerable to the cold weather in the late fall and early spring, Cain said.

Parts of Colorado have experienced temperatures around minus 30 this week. But winter weather of 50 degrees below zero was more likely to zap the beetles.

That kind of weather helped end a big beetle outbreak in Colorado's White River National Forest in the 1950s.

The nation's forests have had bark beetle epidemics but never one this widespread, this fast-moving and this high-it has reached elevations on trees with no natural resistance-according to the Forest Service. The infestation has reached 384,000 acres in the Black Hills in western South Dakota.

Warmer winters and past fire-suppression policies that allowed thick stands of lodgepole pine to grow are among the reasons.

The bugs burrow under the bark and lay their eggs, turning green needles the color of rust as they bore through the tree's vascular system and restrict its ability to draw water. Eventually the needles fall off, and the tree turns gray.

Dead trees have been cut down to reduce the risk of wildfire and prevent pines from injuring people, blocking roads and trails or damaging power lines.

 

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