The Rise of Spruce Beetle in the Colorado Mountains

by Emily Jack-Scott (Garfield County Master Gardener Apprentice) The spruce beetle (Dendroctonus rufipennis) is currently the leading insect responsible for killing trees in Colorado, having usurped mountain pine beetle in 2012 (2017 Report, CSFS). These bark beetles have swept through hundreds of thousands of acres of forested lands in the Colorado Rockies in recent years. Since 2000, close to 2 million acres have been impacted across Colorado. Counties most heavily impacted between 1996-2018 include Hinsdale, Mineral, Saguache, Gunnison, Conejos, and Rio Grande; each experiencing hundreds of thousands of affected acres. (2018 Report, CSFS) Spruce bark beetles are a native species, endemic to the Rocky Mountains. In Colorado, the beetles favor high alpine (above 9,000’) Engelmann spruce, but will also attack Colorado blue spruce and Norway spruce, and at lower elevations. At usual low endemic levels the beetles target dead trees, from windfall events or the like. But once they rise to e