Spruce beetle was the most damaging forest insect pest in Colorado for the fifth consecutive year, based on a 2016 forest health aerial survey conducted by the Colorado State Forest Service (CSFS) and U.S. Forest Service (USFS), Rocky Mountain Region. Douglas-fir beetle populations also continued to expand, while mountain pine beetle, western spruce budworm and Douglas-fir tussock moth populations continue to decline. Every year the CSFS and USFS work together to aerially monitor forest health conditions on millions of forested acres across the state.
Spruce beetle populations continued to cause widespread tree mortality, impacting 350,000 acres of higher-elevation stands of Engelmann spruce statewide. The largest infestations were detected primarily in southern and central Colorado, with more than one-third of those acres “new” or not previously impacted. Blowdown events in Engelmann spruce stands, combined with long-term drought stress, warmer temperatures and extensive amounts of older, densely growing trees, have contributed to this ongoing epidemic.
Since 1996, spruce beetle outbreaks have caused tree mortality on more than 1.7 million acres in Colorado.
The aerial survey also indicated that activity of Douglas-fir beetle, a close relative of spruce beetle that attacks and kills mature Douglas-fir trees, significantly increased on the Western Slope, with 19,000 acres impacted in 2016. Unlike spruce beetle, populations of this pest tend to erupt in numerous smaller pockets, rather than spreading outwardly from a few main population centers. Eagle, Garfield and Pitkin counties, along with most of the Gunnison Basin, were all heavily impacted with pocket activity in 2016.
Conversely, declines in impacted acreage were observed for western spruce budworm, Douglas-fir tussock moth and fungal leaf diseases of aspen trees.
From Forest Business Network: https://www.forestbusinessnetwork.com/67220/spruce-beetle-epidemic-continues-to-expand-kill-trees-in-colorado/