ASPENTIMES.COM — The Roaring Fork Valley experienced a spread of Douglas fir, spruce, and western balsam bark beetles last year but the infestations remained light compared to many other parts of the state, according to the latest assessment.
The U.S. Forest Service and Colorado State Forest Service released results of their 2020 Forest Insect and Disease aerial survey this week. The annual flyover of the state’s forests was pared down last year because of COVID-19 challenges. It covered 16 million acres or about half of prior years. The Roaring Fork Valley was one of the priority areas.
“I can share (that the) spruce beetle has moved into the Aspen area, particularly in the northern reaches of the Elk Mountains,” Dan West, forest entomologist with the state forest service, wrote in an email.
The aerial survey indicated the White River National Forest had about 160 acres of new spruce beetle activity that was detectable from the air. The infestation is likely more widespread, he said, because what can be seen from the air is usually less than what’s occurring on the ground.
The survey also determined that the Douglas-fir beetle infestation has intensified because of the Lake Christine Fire of July 2018 on Basalt Mountain.
“Moderately scorched trees are havens for bark beetles, and the trees along the burn perimeter were likely brood trees for these beetles,” West said.
Forest health assessments are vital because Colorado’s forests have come under pressure from climate change. Warmer temperatures and unpredictable precipitation levels are stressing trees, said Adam McCurdy, forest and climate director at Aspen Center for Environmental Studies.
He said Douglas-fir beetles have been a slow but growing problem primarily down valley from Aspen, with spot infestations in Castle Creek Valley, the ridges north and east of Snowmass Canyon, and the Fryingpan Valley.
“To me, that’s a big and continuing part of the forest health story,” McCurdy said. “I don’t think it’s gotten enough attention in the valley.”
The Douglas-fir beetle problem has been a “slow burn” compared to the mountain pine bark beetle infestation that was so visible in many parts of the state, he said. Large swaths of lodgepole pine trees in the Interstate 70 corridor died and turned rust color during the pine beetle infestation of the late-1990s and early-2000s. The Roaring Fork Valley was largely spared from the mountain pine beetle infestation because of diversity in tree types and age classes.
The aerial survey report includes a map that shows areas of infestation from various beetles. The terrain surrounding the Roaring Fork Valley has what looks like small freckles representing the outbreaks. Other parts of the state are covered with larger blotches representing more widespread infestations.
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