Gunnison County forests dealing with many foes

Spruce beetle poses major threat

Editor’s Note: Last week the News reported on the mountain pine beetle and its presence in local forests. This week, we look at other threats to the forest, with the help of Sam Pankratz, forester for the Colorado State Forest Service.

With all the talk of insects attacking local trees, you’d think we’re in store for a biblical plague. It hasn’t reached that critical stage yet, but there are a number of native and exotic species that take a toll on forest health and have the potential to reach epidemic levels.
According to Colorado State Forest Service forester Sam Pankratz, “Aside from mountain pine beetle, I think we should be most concerned about building populations of spruce beetle. Spruce beetle, another native insect, has already affected more than 400,000 acres in Colorado since the outbreak began in 2003.
“The beetles are concentrated in the high-elevation Engelmann spruce forests of the upper Rio Grande Basin, where aerial survey flights last month provided evidence of further spread of the beetle. Spruce beetles have killed almost all of the mature trees in most Engelmann spruce stands in the San Juan Mountains of southern Hinsdale and Mineral counties,” said Pankratz.
The spruce beetle has flown under (or over) the public’s radar because its effects aren’t as easily seen, due to most outbreaks occurring at higher elevations.
“Spruce beetle outbreaks tend to happen in remote, high-elevation forests and don’t get as much public attention as mountain pine beetles,” said Pankratz. “Experts consider spruce beetles the second-most destructive potential to our forests, behind the mountain pine beetle. Gunnison County is home to large areas of high-elevation spruce forests, causing concern for the beetle’s potential expansion northward into our county. Large windthrow events create the ideal situation for spruce beetle populations to build in down trees.”
Other insects of concern, according to Pankratz, include the Douglas fir beetle, the Ips beetle and the host of secondary insects and diseases associated with these primary insects and diseases.
Insects are not the only things bugging the forest. In recent years, aspen trees are experiencing a phenomenon known as Sudden Aspen Decline (SAD).
“We’ve been dealing with SAD in our district and in southwestern Colorado,” said Pankratz. “It was first observed in the state in 2004, and by 2008 it affected an estimated 17 percent of the aspen forest type in the state.
“Symptoms of SAD include rapid branch dieback,” observed Pankratz, “crown thinning and mortality of aspen trees on a large scale. There’s been new research on the causes of SAD, including predisposing factors such as low elevations, aspect, physiological maturity, and low stand density. Inciting factors include recent drought and higher temperatures during the growing season. Other contributing factors include other insect and diseases commonly associated with aspen stands.”
In addition to native insect populations, there are exotic species posing threats as well, including the emerald ash borer and gypsy moth, which are currently causing concern in the eastern parts of the country. These insects are easily transported in firewood and can even attach themselves to moving vehicles, trailers, and such.
According to Pankratz, the best thing people can do to stay vigilant is educate themselves about the signs of these infestations, and report them to the Colorado State Forest Service 970-491-6303.