As the mountain pine beetle activity declines in Colorado, other bark beetles are on the rise on the Western Slope.
Garfield County has largely escaped the ravages of mountain pine beetle, which infested more than 1,000 acres of ponderosa and lodgepole pine in the high Rockies during the outbreak’s peak in 2008. But the county also hosts scattered populations of the closely related spruce beetle and Douglas-fir beetle, as well as the western balsam bark beetle. Each species targets different conifers, generally killing infested trees.
Spruce beetle infestations have increased year over year since 2008, with around 400 acres affected in 2013. Most of the worst damage has taken place in the Rio Grande National Forest.
“It looks just like Summit County looked five years ago,” observed Jan Burke, a silviculturist for White River National Forest. “It’s very sobering.”
The beetle is also on the rise on the Grand Mesa, and White River National Forest hosts a slow-growing pocket of infested trees in Baylor Park above Four Mile. The latter infestation was likely precipitated by an August 1999 blowdown that toppled between 2,000 and 3,000 acres of spruce, fir and aspen.
According to Burke, spruce beetle damage is also beginning to pop up in areas of the Flat Tops that were hard hit in the 1940s and ’50s. Trees that were saplings at the time are now big enough to be targets themselves.
As of 2012, however, the less virulent western balsam bark beetle was the primary offender throughout White River National Forest. Douglas-fir beetles have also spread at lower altitudes, particularly within the narrow walls of the Crystal River Valley.
“We don’t have very much Douglas-fir, but what we do have is getting hit pretty hard,” said Burke.
The Forest Service is doing its best to mitigate impacts and accelerate the renewal process. Around 90,000 seedlings are planted each year in White River National Forest. Saplings are fairly resistant to bark beetles, which usually go for mature trees. Spruce beetles often target the largest specimens, and since spruce is slow-growing, seedlings benefit from the head start in infested stands and at-risk areas.
Crews have also had some success using anti-aggregating pheromone packets containing MCH (3-methylcyclohex-2-en-1-one) to deter Douglas-fir beetles in campgrounds, ski areas and other key areas.
In the end, however, it’s impossible to protect the entire forest.
“I would hope that we learned from the mountain pine beetle infestation that stopping these infestations is not a reasonable objective,” said Burke. “Chasing bark beetles after they’ve already grown to epidemic proportions won’t get us anywhere.”
Burke emphasized that the beetles are native to Colorado forests and are present in some level at all time, and infestations are part of the natural cycle.
“The hard truth is that all trees at some point die,” Burke said.
Still, the forests provide critical habitat for a wide range of wildlife, as well as a practical and recreational resource for people. Burke worries that falling dead trees will render some areas unsafe or unusable in upcoming years. Damage from beetles can also increase the chance and severity of fire.
In the end, Garfield County and the Roaring Fork Valley are unlikely to see the sort of landscapewide mortality many locals will remember along the Interstate 70 corridor during the height of the mountain pine beetle outbreak. Our forests are more diverse, and while climate change can aid beetles’ proliferation, a longer growing season also has its benefits. Burke has noticed a usually hit-or-miss spruce cone crop almost annually in recent years. That means more saplings in the wild as well as more stock for federal nurseries.
“Mother Nature does so much better a job of balancing things than we do,” she said.
“The hard truth is that all trees at some point die.”
silviculturist, White River National Forest