Bark beetle infestations once again on rise in Boulder County

Monday, January 14, 2019

Bark beetle infestations once again on rise in Boulder County.

BOULDER, COLORADO — Since 2000 spruce beetle outbreaks have wreaked havoc on more than 1.8 million acres in Colorado, affecting approximately 40 percent of the spruce-fir forests in the state.

Although the new acreage affected by these bark beetles has declined each of the past four years, according to a new aerial forest health survey conducted by the Colorado State Forest Service and U.S. Forest Service, 178,000 acres of high-elevation Engelmann spruce were newly affected in 2018, including 500 acres in northwest Boulder County.

While this uptick is largely attributed to the low levels of precipitation in 2017, the second driest year in Colorado's history according to the Colorado Climate Center, representatives from the Colorado State Forest Service said they hoped the spread of these beetles would once again slow in 2019 as water levels increase.

"Spruce beetle built up its population during the drought of 2002 in Routt County and been able to move through susceptible Engelmann spruce populations at high elevation in Roosevelt National Forest and into Rocky Mountain National Park, but not at a record pace," said Dan West, the entomologist tasked with coordinating the aerial survey for the Colorado State Forest Service. "Snowpack in the South Platte River Basin is at 110 percent so there's not a tremendous cause for alarm, but it's certainly enough to keep an eye on it."

The main concern with the current trend is that losing Engelmann spruce trees at high elevation will limit the snowpack shaded by these trees in previous years, causing the spring runoff to occur faster and increasing the risk of wildfires in late summer.

"Forestry Distributing's Synergy Shield MCH, Douglas-fir and Spruce Beetle Repellent uses MCH – a naturally occurring anti-aggregation pheromone of the Douglas-fir beetle to protect living trees from attack by Spruce, and Douglas-fir beetles. It is also used to prevent the build-up of populations on logs, stumps, and fallen trees. MCH sends a message that the tree is full and that beetles should look elsewhere for a suitable host."

While there is nothing a home or landowner can do to stop the spread of the beetles, they can take preventive measures to try and slow the spread.

"Colorado's forests are important to the ecological and economic health of our state," said Mike Lester, state forester and forest service director. "Our efforts in partnership with the U.S. Forest Service ensure that we understand the condition of our forests, so we can design the best treatments to enhance forest health."

The best thing property owners can do, according to the Colorado State Forest Service, is carefully examine any pine trees on their property for signs of infection. Removing beetle-infested trees early will have a positive impact on forest health, reduce the number of hazard trees on the property, and decrease potential wildfire danger.

To determine whether a tree is still infested, property owners should look for pitch tubes or small mounds of reddish-orange boring dust on the main tree trunk and peel back an area of bark the size of a deck of cards just above the tubes or dust.

If there are live insects, eggs, or larvae the tree is obviously still infested and will need to be treated before moving the wood.

If there is blue staining but no insects, or small circular exit holes on the outer surface of the bark, then the insects have already flown from the tree and the wood is safe to be moved.

To properly dispose of an infected tree landowners can take it to a sorting yard, to be chipped and spread out in a thin layer so it drys quickly and doesn't attract other kinds of bark beetles, or it can be totally stripped of its bark so beetle larvae are exposed to the air and sunlight.

Infected logs can also be laid out in a single layer and covered with a clear plastic sheet in a very sunny, south-facing location for at least eight weeks in the fall to cook the beetles to death. Infested wood can also be used for firewood if needed, but it must be burned before July, when any remaining beetles could fly off to live trees.

While there are also preventative sprays and pheromone pouches that can help a tree defend itself from beetles, there is no guarantee it will save a tree.

"Spraying trees to prevent an attack from mounting pine beetles is effective when protecting a small number of high-value pine trees, but it is not recommended on a large scale," Ingrid Aguayo, an entomologist for the Colorado State Forest Service, wrote. "If you live in an area faced with a high beetle population, it is only realistic to choose a few individual trees that you want to save. No single preventive method offers a comprehensive solution, and, many times, different management methods work best when used as part of an integrated pest management strategy."

John Spina: 303-473-1389, or

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