Mountain pine beetles (Dendroctonus ponderosae) may be familiar to residents who lived here during the epidemic of this insect two decades ago. Once the state’s most deadly forest pest, the mountain pine beetle affected about 80 percent of pine forests in Colorado from 1996 - 2014.

Outbreaks of this native bark beetle still pop up in pine forests across Colorado, enabled by overly dense forests and ongoing drought conditions. Currently outbreaks are occurring along the Interstate 70 corridor near Idaho Springs and Black Hawk, as well as increased activity of this insect in the northern Black Forest near Colorado Springs. This time around, this insect is affecting primarily ponderosa pines.

Why should we care about mountain pine beetles?

They’re just tiny beetles--are they really that bad? Once infected, a tree will die in one year. Talk to residents of Missouri Lakes, some lost 30 - 40 trees in one season. The loss of trees is expensive for landowners to manage. Tree losses also impact property values, can increase wildfire danger and present a hazard when important windbreaks are diminished due to dead and fallen trees.

What can landowners do right now?

December is an ideal time to check pine trees for the presence of mountain pine beetles (MPB). Look for green trees that have signs of new infestation. It’s important to note that if the tree needles are already brown, the beetles are no longer in the tree, and treatment options for a dead tree are more for safety and/or fire mitigation. Green trees are those that we are discussing here.

Signs of mountain pine beetle infestation

1. Pitch tubes: They look like popcorn, but they’re actually globs of sap. A healthy tree can flush beetles out, but if you see multiple pitch tubes or tubes that are red or pink, there’s a good chance that beetles have infested the tree.

2. Frass: Look around the base of the tree and in crevices in the bark. If you see sawdust, it means the beetles have been boring into the tree’s bark.

What to do next

After MPB infests a tree, there is only one best practice: Remove the tree to kill the beetle larvae which are under the bark of the tree for the winter. Mark the trees for removal and make a plan to get them out by next spring. At the very least, cut the tree now so it has time to dry out all winter, which may kill the beetle larvae. Better practices include hauling the tree out, debarking the tree, or chipping it. Chipping and debarking will kill the beetle larvae that are in the “hot” infested tree, which will reduce the population of beetles next summer.

If you’re hauling the infested wood away, make sure you take it outside of the forest, to a site at least one mile from susceptible pines (ponderosa, lodgepole, and limber). Another option is to contact Gilpin Public Works at 303-582-5004 to make an appointment to drop off your “hot logs” at the slash site. They will chip the logs.

Learn more at a free educational workshop

Attend a free Mountain Pine Beetle Workshop on January 10, 2024, at 6:30 p.m. at the Gilpin Public Library or online. Gilpin CSU Extension Educator, Jennifer Cook, and Ben Pfohl, Colorado State Forest Service, will provide an overview of the life cycle of the mountain pine beetle, discuss the signs and symptoms of attack on trees as well as detail preventative management options for Gilpin residents. A map of current infected areas in Gilpin County will be viewed. The webinar will be recorded and posted on Gilpin CSU Extension website for those who cannot attend.

Register for online attendance (registration not required for in-person attendance) on the Gilpin Extension website at https://gilpin. extension.colostate.edu/classes/.

To contact us, call or email Gilpin CSU Extension with your questions at 303-582-9106 or Jennifer.cook@colostate.edu.

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