The health of our waters is the principal measure of how we live on the land — Luna Leopold
Aerial Survey: Though Declining, Spruce Beetle Remains Most Damaging Forest Pest — @CSFS_Outreach
The spruce beetle remains the most damaging forest pest in the state for the ninth consecutive year, based on a 2020 aerial detection survey. Photo credit: Dan West/Colorado State Forest Service
Here’s the release from the Colorado State Forest Service:
Forest managers are working together to address continued outbreaks of insects and disease in Colorado’s forests, including the spruce beetle, which remains the most damaging forest pest in the state for the ninth consecutive year, based on a 2020 aerial detection survey led by the USDA Forest Service, Rocky Mountain Region, and Colorado State Forest Service.
Every year, the agencies aerially monitor forest health conditions on millions of forested acres across the state. Today, the agencies released the results of last year’s aerial survey and survey map.
Due to pandemic safety protocols in 2020, trained aerial observers with the USFS and CSFS only flew over priority areas where there was a likelihood of forest pests causing widespread tree mortality.
In total, they monitored 16.3 million acres from the air, compared to 30.2 million acres in 2019.
Because of the reduced acreage observed, total numbers of affected acres are not included in the findings or in the forthcoming 2020 Report on the Health of Colorado’s Forests since comparisons between 2020 and other years are not possible.
Impacts from Native Bark Beetles
Despite the modified flights, observers were able to detect and track pests infesting areas of forests that were previously unaffected, including the spruce beetle and Douglas-fir beetle. While the intensity of these two native bark beetles decreased in 2020, they continue to infest and kill previously unaffected stands.
The Spruce beetle affects high-elevation Engelmann spruce. Primary areas impacted by this insect include newly infested forests in eastern Gunnison and western Chaffee counties. Both counties are experiencing severe, intense infestations. Spruce beetle populations also increased in Hinsdale, San Juan and La Plata counties. Beetle outbreaks in Huerfano and Custer counties continue to expand as well, though not as rapidly. In Grand County, the intensity of infestations has declined from past years as the beetle continuously depletes large-diameter spruce trees. Since 2000, the spruce beetle has affected at least 1.88 million forested acres in Colorado.
The Douglas-fir beetle continued to invade Douglas-fir trees in central and southern Colorado, particularly in Gunnison, Saguache, Hinsdale and Mineral counties, where infestations are severe.
Spurred by Drought Conditions
Weather continues to play an important role in creating conditions that exacerbate the activity of spruce and Douglas-fir beetles, as well as other forest pests, in Colorado. The amount of precipitation and daily temperature patterns affect how well trees can ward off pests to remain healthy and resilient. In 2020, winter and spring had average precipitation amounts. Thereafter, severe and extreme drought conditions across most of the state occurred through the summer and fall, further weakening trees and intensifying infestations of bark beetles and other forest pests.
“Unfortunately, our dry conditions are optimal for insect epidemics and tree diseases in many parts of the Rocky Mountains,” said Tammy Angel, Acting Regional Forester for the USDA Forest Service, Rocky Mountain Region. “Where possible, managing forests for age and species diversity can increase resiliency while ensuring diverse wildlife habitat, cleaner air and water, timber and grazing resources, and greener, safer landscapes for recreation.”
Spurred by drought conditions, the roundheaded pine beetle and associated native bark beetles continue to affect ponderosa pine forests in Dolores and La Plata counties in southwest Colorado. The intensity of this activity remains high in localized areas of the San Juan National Forest. Further to the south, pockets of affected areas within La Plata County are expanding.
The aerial survey also revealed that western spruce budworm continues to be Colorado’s most damaging and widespread forest defoliator. Budworm infested forests in south-central Colorado continue to experience intense disturbance. Over several years, defoliation from this insect may weaken a tree to the point where bark beetles can easily overcome the tree and kill it.
“Colorado’s forests are vital to the economic and ecological health of our state,” said Mike Lester, state forester and director of the Colorado State Forest Service. “Our partnership with the USDA Forest Service on the aerial survey offers another great example of how we can effectively address forest health issues that span property boundaries by working together, like bark beetle outbreaks. With information from the survey, we better understand the health of our forests and can focus our efforts where they’ll make the biggest impact.”
The aerial survey exemplifies the agencies’ continued support for shared stewardship and the Memorandum of Understanding signed in 2019, which establishes a framework for federal and state agencies to work collaboratively to accomplish mutual goals and respond to ecological, natural resource, and recreational challenges and concerns for the 24.4 million acres of forestlands in Colorado.
For more information on the insects and diseases of Colorado’s forests, and support for landowners seeking to achieve healthier forests, contact your local CSFS field office or visit http://csfs.colostate.edu.
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…
“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.
Map via the Carbondale and Rural Fire Protection District.
“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 downvalley from Aspen, with spot infestations in Castle Creek Valley, the ridges north and east of Snowmass Canyon and the Fryingpan Valley…
McCurdy said Douglas fir trees have proven in the past to be resilient because they are hardier in a warmer climate. Recent droughts and warm temperatures have stressed them.
West agreed that drought in the Roaring Fork Valley and throughout Colorado has made Douglas firs more vulnerable to beetles. Last year’s weather pattern added to the problem.
McCurdy pointed out that intense Douglas-fir beetle infestations are on the doorstep of Pitkin County, in eastern Gunnison County.
In addition to Douglas-fir infestations, the aerial survey map shows small outbreaks of western balsam bark beetles in higher elevations of the Independence Pass corridor as well as Castle and Maroon creek valleys. Sub-alpine fir trees are vulnerable to the western balsam bark beetles. There are also a few small pockets of spruce beetle infestations in the Roaring Fork watershed.
White River National Forest officials were concerned about a potential spruce beetle outbreak after a landmark avalanche cycle in March 2019. The slides wiped out untold acres of mature spruce and other trees in areas such as Conundrum Creek Valley and Lincoln Creek Valley.
West said there is limited potential for the debris piles to host an infestation…
The Colorado State Forest Service also identified disease in Colorado’s signature aspen trees as another emerging problem in 2020, largely because of drought.
McCurdy said there is ample evidence of aspen stands experiencing problems in the Aspen area: the Cemetery Lane side of Sunnyside Trail, upper Buttermilk and the west side of Castle Creek Valley downvalley from Toklat Lodge among them.
The White River National Forest announced Thursday a major proposal for a decades-long aspen management plan. The 2.3-million-acre forest contains an estimated 600,000 acres of aspen trees. About 375,000 acres are targeted for timber harvesting and prescribed fire to maintain and expand aspen stands.
A high-elevation spruce beetle-affected forest. Photo credit: Seth Davis via Colorado State University
Nearly every mature spruce tree has been killed by spruce beetle in this area of the Rio Grande National Forest in southwest Colorado. (Credit: U.S. Forest Service; photo: Brian Howell)
Some of the threats climate change poses to Colorado: shorter winters, forests killed by invasive pine beetles, and habitat loss for the Pika, which thrives in cold, high-altitude environments. Photo credit Conservation Colorado and Western Resource Advocates.
Area above Dillon Reservoir, seen in the upper left, before thinning and then after. Photos/Denver Water
Forest ecosystems around the world are under the gun from climate change, development, insect invasions and conversion to agriculture. This stand of lodgepoles in Colorado was clear cut after pine beetles killed most of the trees.
A scene in Summit County, between Farmers’ Corner and Summit Cove, overlooking Dillon Reservoir, both pre-treatment and afterward.
