Bark beetles and root rot are natural in Colorado’s forests, but when combined with the stress of years of serious drought conditions, the three have formed a deadly blow for many evergreen trees.

The recently released 2022 Report on the Health of Colorado’s Forests, the annual assessment produced by the Colorado State Forest Service, shows the western balsam bark beetle is the latest native bug to take a bite out of the tree population, turning subalpine fir red and dead.

Bark beetles continue to cause the greatest forest health concerns in Northwest Colorado, both through the impacts of beetles currently infesting trees and those that killed trees decades ago, according to the 2022 report.

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During aerial surveys, experts from the State Forest Service recorded approximately 18,000 acres of trees affected by the western balsam bark beetle in the greater Routt County area during flights conducted in summer 2022, an increase from about 11,500 acres affected in 2021.

Newly infested trees can be removed prior to the adult western balsam bark beetles emerging the following year to infest other trees. However, management is a challenge because of the low value of the wood to offset treatment costs, infestations that are spotty and unpredictable, and remote and steep terrain at high elevations that is difficult to access. — 2022 Report on the Health of Colorado’s Forests

That translates to an additional approximately 6,500 acres affected in one year.

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“It will take several years of adequate precipitation for subalpine fir to recover their defenses to fend off the western balsam bark beetle, which attacks young as well as mature trees,” according to the report.

The current rise in balsam beetle follows the well-known epidemic from the mountain pine beetle, also a native bug, that decimated acres of trees from the early 2000s through mid-2008, said Carolina Manriquez, a State Forest Service forester in Steamboat with 20 years of experience in the field. The dead trees, either fallen or standing dead, from that mountain pine beetle epidemic fuel wildfires today.

That is why the 2022 forest report lists the top three statewide forest health issues as insects and diseases, living with wildfire, and watershed protection. Those three agents working together on the landscape intertwined create a continuing threat to forests in the greater Routt County area, Manriquez said. Forested land represents approximately two-thirds of Routt County.

The spruce beetle, also a native bug, has continued to damage the trees since the 1990s with about 100,000 acres affected in Routt County so far, Manriquez said. That includes spruce beetle growth after a blowdown of some 4 million trees in October 1997 in North Routt.

“Spruce beetles have always been around, but after the blowdown, populations exploded,” Manriquez said.

Spruce beetles continue to affect trees from Rabbit Ears Pass to downtown Steamboat Springs and are creating pockets of damage largely along high elevation areas, she said.

The mountain pine beetle is still present in the forests but has eaten through much of its food source of trees, particularly lodgepole pine, the forester explained.

The latest battle with the western balsam bark beetle, a native bug, became more noticeable about five years ago, and even more prevalent in the past two to three years in pockets based on drought, Manriquez said.

The complication with western balsam bark beetle is the native subalpine fir trees those bugs prefer are sappy and are not favored for construction or firewood. Subalpine fir trees are not studied as much as other trees because they not marketed as much as other species like lodgepole pine.

“Newly infested trees can be removed prior to the adult western balsam bark beetles emerging the following year to infest other trees,” according to the state report. “However, management is a challenge because of the low value of the wood to offset treatment costs, infestations that are spotty and unpredictable, and remote and steep terrain at high elevations that is difficult to access.”

In 13 years of observations in Routt County, Manriquez is “definitely seeing our forest health declining.”

“Forests are dynamic; they are ever-changing and exacerbated by climate change and drought. Trees are more stressed, so they are more susceptible to insects and disease,” Manriquez explained. “Some of the aspen stands are also in decline because of the same reasons.”

The decline in forest health worsened by prolonged drought conditions continues despite the more abundant snowpack this winter.

“That prolonged drought and dry, hot summers prior to 2022 weakened defenses in trees leaving them susceptible to attack from bark beetle,” said Manriquez, who encourages land and homeowners to water their landscaping trees during hot weather.

With the decline in trees from disease, beetles and wildfire, reforestation is critical, the annual report notes. Demand is growing rapidly for nursery-grown seedling trees and shrubs including from the CSFS Nursery. Last year, that state nursery started upgrades to its facilities in Fort Collins to ramp up production with funding approved by the state legislature.

“Colorado needs seedling trees to reforest burned areas, store carbon and build climate-resilient watersheds and forests,” according to the report.

Landowners can contact the Colorado State Forest Service for advice when they see trees on their property starting to run red. If dead trees are removed sooner rather than later, that may reduce the expansion of beetles in a stand of trees.

“We need to work together as neighborhoods and HOAs to address forest health issues because they are also wildfire issues,” Manriquez said.