THE BEETLES HAVE FLOWN – NOW WHAT?

In January’26, a blog post titled “Mountain Pine Beetle Infestation 2026” appeared in this blog.

https://planjeffco.org/mountain-pine-beetle-infestation-2026/ 

Eight months later, sometime toward the end of summer, the Mountain Pine Beetles (MPBs) will have flown. They began their yearly exodus around the middle of June. A day or two after the beetles flew, the females began to burrow under the bark of pine trees – mostly Ponderosa and lodgepole pines in Jefferson County.

Once safely under the bark, the females were joined by the males, and together they began tunneling and feeding in the cambium layer, the “live” portion of the tree’s bark, eventually girdling the entire circumference of the tree, cutting off the tree’s ability to move nutrients from the roots to the rest of the tree structure above the beetles’ chambers.

During the summer and early fall, as the host tree begins to die, the beetle pair will create galleries, side chambers, within which the female will lay dozens of eggs. Once the adult beetles have completed their task, they will die, but the eggs will complete the MPB life cycle. Over winter, the eggs will develop into larvae and grow into adulthood, becoming the next generation of MPBs. In the following late spring to early summer, this new generation will emerge from the now-fading pine trees, and fly.

Once the beetles have flown, the tree no longer hosts live beetles. There’s no need to apply any preventative; it’s a standing dead tree. It’s no longer possible for it to host a new generation of MPBs. The trees that are hosting live beetles and eggs are those that, according to JeffCo, must be managed. Within Jeffco, the MPB is a regulated pest, and landowners are responsible for inspecting their forests and controlling the MPB whenever it is found.

As an Open Space Parks visitor, you’ve surely encountered “forest health management” operations in some of the parks. Occasionally, an entire park will be closed to visitors for an extended period of time while infested and some dead trees are removed, as per County regulations.  If you have questions or concerns regarding the Open Space Forest Health Management Plan, read more at https://www.jeffco.us/DocumentCenter/View/33433/JCOS-Forest-Health-Plan-

An infested tree, one which is hosting live MPB larvae, must be felled; that should happen between October and mid-April. Chipping should be completed before the first of June. Do not move beetle-infested wood! Moving wood that contains beetle infestation is one way the beetles can infest new areas.

For solar treatment: remove and scatter the limbs. Cut the trunk into 4-foot or shorter lengths. Elevate the logs on pallets, placing them side-by-side in a full sun location. Wet the logs. Cover with a CLEAR plastic tarp of at least 6-mils in thickness. Dig a trench around the logs, bury the tarp’s edges in the soil, ensuring the tarp stays in place for at least 3 months. If the tarp tears, repair so the seal is fully intact. Ideal temperature beneath the tarp needs to be 120F, otherwise this method may not be effective. Carefully dispose of the plastic after use; do not try to reuse.

For debarking: remove and scatter the limbs. Remove the bark on the log – a chainsaw attachment, a knife or an ax will work. If the felled tree is allowed to dry for a week, debarking is easier. Once the bark is removed and scattered, the wood can be moved.

For chipping: trees should be chipped immediately after felling. Chips left onsite should be scattered so that they do not exceed a depth of 4 inches.

For additional methods and restrictions, especially for larger properties, refer to JeffCo’s MPB Factsheet at https://www.jeffco.us/DocumentCenter/View/34067/Mountain-Pine-Beetle-PDF

JeffCo has SLASH sites available for disposal, some of which are open through the end of October. MPB infested logs will be accepted at the Tincup Ridge SLASH Yard only, and then only after September 30. For more information on the SLASH sites, go to jeffco.us/SLASH.

While all this forest management, which falls into the lap of the individual landowner, seems like a huge burden, it’s going to take a large-scale, concerted effort to arrest the MPB infestation. According to a 2025 study by the Colorado State Forest Service, about one-third of Jefferson County is populated by Ponderosa pines; about half of these trees fall into the medium (6-12 inch) to very large (18+ inches) diameter range, the ideal hosts for the MPB. Driving west on I-70 or south on Hwy-285, the sight of entire hillsides of “red and dead” are what we can expect in our own foothills if we don’t try to quell the MPB infestation. It will take a village, and the larger the village, the better the chance we have of saving some of our beloved Ponderosa and lodgepole pines.

References:

https://csfs.colostate.edu/forest-management/forest-health-report-2025/mountain-pine-beetle/

https://www.jeffco.us/4561/MPB—TreatmentOptions

https://www.jeffco.us/2738/Mountain-Pine-Beetle

https://www.jeffco.us/2493/Slash-Collection

Miss Mountain Manners says “For the love of the land, please inspect your trees, even if you don’t live in the mountains or in the rural parts of the County. MPBs don’t recognize city boundaries. When there’s an infestation, they’ll attack almost any conifer.”