The Gilpin County CSU Extension Service held a workshop on the pine beetle outbreak in Gilpin County on January 10, 2024, at the Gilpin County Library starting at 6:30 p.m. The purpose of the workshop was to talk about the developing pine beetle outbreak, identification and treatment of infected trees, and preventive measures that can be taken before a tree is infected with pine beetles.

The workshop was led by Gilpin County CSU Extension Agent Jennifer Cook, who described the two species of pine beetles (Mountain Pine and Ips) that are active in the area and their biology. Colorado State Forest Forester Ben Pfohl presented the sections on treatment options and preventive measures.

After a decade of being dormant in the area, Mountain Pine Beetle outbreaks are occurring in Gilpin County. The most serious outbreak is near Black Hawk in Four-mile Gulch behind the Ameristar Casino. The beetle infestation is on both sides of Dory Hill Road and moving north up the hill at an increasing rate. Infected trees have also been identified in other parts of the county.

Cook said that the Mountain Pine Beetles seem to be targeting Ponderosa Pine this time around. In the 2008-2012 pine beetle outbreak, the pine beetles tended to infect Lodgepole Pine stands. In general, both species of beetle prefer larger, older trees. Trees with a diameter of six inches or greater are the most at risk of being attacked.

Cook showed examples of beetle galleries under the bark of a tree, where the beetle larvae live. A female beetle will bore through the bark of a tree and deposit eggs between the cambium and the heartwood. When they hatch, the larvae will live on the cambium and eat vertically or horizontally through the underside of the bark all winter. In late summer, the larvae will metamorphose into pupae and then adult beetles. The adult beetles will exit the infected tree and fly away to start their cycle again in another tree.

Heavily infected trees lose the ability to transport fluids between the needles and the roots because the cambium fibers have been destroyed. They will usually die within a year of being infected. Cook said that trees with red tops and brown needles are already dead, and the beetles have probably already left. Trees that still have green tops but show signs of being infected are the ones that Cook said need to be treated. Signs of infection include pitch tubes, beetle boreholes, and sawdust at the base of the tree.

During his presentation Pfohl emphasized the need to treat infected trees before the larvae pupate. The best times to treat wood are in the winter and early spring. Treatment involves more than just cutting the trees down, because the larvae can live a long time under the bark. Pfohl recommended calling Public Works (303-582-5004) and arranging to have the logs dropped off at the Slash Yard. Gilpin County has controls for handling “hot” – i.e., infected – wood.

Other treatment methods include debarking the log with a Log Wizard, wrapping the logs in plastic to bake the beetles, burying the logs under six inches of dirt so the beetles can’t fly, and chipping the logs, so the larvae are exposed and die when they are dried out.

Woodpeckers are one of the natural controls on beetles. Woodpeckers can eat their weight in beetles every day. Hanging suet packs out near the bird feeder will keep woodpeckers around to help beetle control if they are still stoppable.

Other prevention measures include pheromone packs and spraying trees with insecticides. Pheromone packs are a chemical product that confuses the beetle. It is known to have some efficiency if the infestation is light.

There is a 99% chance that a tree that is sprayed with insecticide will survive, but the poisons are indiscriminate and will kill other insects, like pollinators. Spraying is controversial because of the potential damage to other insects, but it will save critical trees that are important to a property.

Cook has information on both prevention methods on the Gilpin CSU Extension website (gilpin.extension.colostate.edu) and residents can contact her directly (303-582-9106 or Jennifer.Cook@colostate.edu) for more information.

Cook finished the workshop by stressing the importance of engaging in actions at the property owner level to slow the spread of the outbreak. She said that the October to March period is the best time to identify, cut, and treat infected trees.

Pheromone packs need to be ordered early so they arrive in time. Appointments for certified sprayers also need to be made early in the year because they can only spray when there is no wind so there are a limited number of slots available.

Cook took the long view that these outbreaks come and go, but healthy forests can survive them.