Rainbow Hill

Protecting Rainbow Hill, Together

Bark Beetles & Forest Health

How to identify local beetle threats, protect priority trees and manage our changing forest

Mountain Pine Beetles and Forest Health

Source: CSFS

Protecting Rainbow Hill’s Trees
Bark beetles are a natural part of Colorado’s forest ecosystem, but drought, crowded forest conditions, tree stress and favorable weather can allow populations to increase rapidly. Mountain pine beetle activity has been rising in Jefferson County since 2023. Across nine Front Range counties, the Colorado State Forest Service documented 5,544 acres of affected ponderosa pine forest in 2025, compared with 2,236 acres in 2024, an increase of approximately 148 percent.

Mountain pine beetle is currently the primary concern for many Front Range communities, but it is not the only beetle capable of killing trees. Douglas-fir beetle, Ips engraver beetles and other forest insects can produce similar symptoms. Correctly identifying both the tree and the insect is essential because different beetles attack different tree species and require different management methods and timing.
Ponderosa Pine vs Douglas-fir

Start by Indentifying the Tree

Source: CSFS

A beetle should not be identified solely by the color of a dying tree. Begin by determining the tree species.
 

Ponderosa Pine


Ponderosa pine is one of the primary mountain pine beetle hosts in Jefferson County.

Common characteristics include:
  • Long needles grouped in bundles of two or three
  • Cones with sharp prickles
  • Mature bark that breaks into reddish or orange-brown plates
  • A pine-like shape with needles frequently concentrated near branch ends


Douglas-Fir

Douglas-fir beetle attacks Douglas-fir trees, not ponderosa pine.

Common characteristics include:
  • Soft, flat needles attached individually to the twig
  • Needles that are green on both sides and narrow where they connect to the twig
  • Hanging cones with distinctive three-pointed bracts extending between the scales
  • Thick, deeply furrowed bark on mature trees

The three-pointed bracts on Douglas-fir cones are often described as resembling a mouse’s hind legs and tail.

Understanding the Different Beetles

Source: CSFS
Mountain Pine Beetle

Mountain Pine Beetle

Mountain pine beetle attacks pine trees, particularly ponderosa, lodgepole and limber pine. In Jefferson County, ponderosa and lodgepole pine are the most commonly affected species. Adult beetles generally emerge and attack new trees from July through mid-September, although local timing can vary with elevation and weather.

Signs may include:
  • Popcorn-shaped resin masses called pitch tubes
  • Pink, white or brown pitch on the trunk
  • Fine boring dust in bark crevices or around the tree’s base
  • Woodpecker damage and pieces of bark on the ground
  • Small exit holes
  • Galleries beneath the bark
  • Needles changing from green to yellow and then rust-red

Needle discoloration is a late symptom. The crown commonly begins changing color eight to ten months after a successful attack, and the beetles may already have left the tree by the time it turns red.
Douglas-Fir Beetle

Douglas-Fir Beetle

Douglas-fir beetle is a native bark beetle that primarily attacks mature Douglas-fir. Populations can increase in forests affected by drought, overcrowding, fire damage, insect defoliation, root disease or large amounts of recently fallen Douglas-fir. Unlike mountain pine beetle, Douglas-fir beetle can reproduce in fallen or recently cut trees and later move into standing trees.

Signs may include:
  • Reddish-brown boring dust in bark cracks or around the base
  • Clear or white resin streaming down the trunk, although resin may not always be present
  • Woodpecker activity and bark removal
  • Small exit holes
  • Vertical galleries beneath the bark
  • Groups of Douglas-fir trees fading from green to rust-red

Douglas-fir needle discoloration often appears approximately one year after the initial attack, frequently after adult beetles have already emerged. The lack of obvious pitch tubes can make Douglas-fir beetle more difficult to recognize than mountain pine beetle.
Ips Engraver Beetle

Ips Engraver Beetles

Colorado has several Ips beetle species that attack pine and spruce trees. Ips beetles generally target stressed, damaged or recently transplanted trees and can reproduce in fresh logs, slash and newly cut branches. Several generations may develop during one season.

Signs may include:
  • Yellow or reddish-brown boring dust
  • Small exit holes
  • Woodpecker damage
  • Individual branches or the top of the tree fading first
  • Damage associated with recent pruning, thinning or accumulated slash

Unlike a successful mountain pine beetle attack, an Ips infestation may initially affect only part of a tree. However, repeated attacks can eventually kill the entire tree. Freshly cut pine and spruce material should be properly managed so wildfire-mitigation work does not unintentionally create Ips breeding habitat.

Important: A Red Tree is Not an Early Warning

Waiting for a tree to turn red can eliminate opportunities to stop beetles from emerging and moving to nearby trees. Residents should inspect green trees for pitch, boring dust, woodpecker activity and other early signs rather than relying only on crown color.

A green tree can already be successfully infested. A red tree often represents an attack from the previous season.

 

What to Do if You Suspect Beetle Activity

 
Understand the Current Situation

Rainbow Hill and the surrounding Front Range are experiencing a rapidly expanding mountain pine beetle outbreak. Mountain pine beetle activity in Jefferson County has increased steadily since 2023, and beetle-affected acreage across nine Front Range counties grew by approximately 148% between 2024 and 2025. At this stage, no individual homeowner, neighborhood or single treatment project can stop the broader regional outbreak.

Our focus must therefore shift from attempting to protect every pine tree to identifying and protecting the healthy trees that are most important to each property and to the community. These may include trees that provide privacy or shade, support slope stability, contribute to defensible space, screen a home or hold particular personal value.

Removing and properly treating currently infested trees is still important. It can reduce the number of beetles emerging from an individual property and may help lessen immediate pressure on nearby healthy trees. However, removal alone will not halt an outbreak occurring across thousands of acres.


Recommended Actions

  • Identify the tree species. Determine whether the affected tree is a pine, Douglas-fir, spruce or another conifer. Different beetles attack different trees and require different management strategies.
  • Inspect green trees, not only red ones. Look for pitch tubes, boring dust, woodpecker damage, resin, bark loss and small exit holes. A green tree may already be successfully infested, while a red tree often represents an attack from the previous season.
  • Select the trees you most want to protect. Prioritize a manageable number of healthy, high-value trees rather than attempting to treat an entire forested property.
  • Consult a qualified forestry professional. Ask a forester, certified arborist or experienced forestry contractor to confirm the pest, evaluate whether the tree is already infested and recommend an appropriate treatment plan.
  • Treat healthy priority trees before beetle flight. Preventive bark sprays remain the most reliable chemical option for protecting individual, unattacked trees when applied correctly before adult beetles begin flying. The Colorado State Forest Service recommends these treatments for selected high-value trees, not for entire properties or forested landscapes.
  • Remove or properly treat actively infested trees. Infested material should be chipped, debarked, treated, burned where legally permitted or transported to an approved location before beetles emerge.
  • Do not move untreated wood. Transporting infested logs or firewood can carry beetles into new areas.
  • Coordinate with neighbors. Treatment decisions made across adjacent properties can protect priority trees more effectively and support a healthier, more resilient forest over time.

The realistic goal is not to stop the regional outbreak. It is to protect the trees that matter most, reduce avoidable losses, manage hazardous trees and help Rainbow Hill’s forest recover in a healthier and more resilient condition.

Managing Mountain Pine Beetle

Source: CSFS

Once a pine has been successfully infested by mountain pine beetle, the tree cannot be saved. Management should focus on treating or removing the infested material before adults emerge and protecting selected healthy trees nearby. Appropriate disposal methods may include chipping, debarking, approved solar treatment, burning where legally permitted or transporting material to an approved disposal location.

Preventive insecticides and products containing verbenone may help protect selected healthy, high-value trees when applied before beetle flight. These products do not cure a tree that is already infested. Verbenone may also become less effective when beetle populations are high, so treatment decisions should be made with a qualified forester, arborist or licensed pesticide applicator.

Managing Douglas-Fir Beetle

Source: CSFS

Long-term management focuses on maintaining healthy, appropriately spaced Douglas-fir stands and promptly addressing infested, wind-thrown or recently cut material. Management options may include thinning, removing infested trees, solar treatment, trap trees, preventive insecticides and MCH pheromone packets.

Douglas-fir beetle can begin emerging earlier in the year than mountain pine beetle. MCH packets and other preventive treatments must therefore be installed before the local Douglas-fir beetle flight period. Residents should not use mountain pine beetle treatment dates as a substitute for Douglas-fir beetle guidance.

Beetle-Killed Trees and Wildfire Risk

Source: CSFS

The relationship between beetle mortality and wildfire is more complicated than simply stating that dead trees cause wildfires. Fire behavior depends heavily on weather, wind, fuel moisture, forest density and the amount and arrangement of live and dead vegetation.

Recently killed trees with red needles can have very dry crown fuels, while older gray trees gradually lose their needles and contribute branches and woody material to surface fuels. Dead standing trees can also create falling hazards and interfere with firefighter access. Regardless of the stage of beetle activity, home hardening and defensible space remain the most effective measures for reducing a structure’s vulnerability to embers and surface fire.

Local and Regional Resources


 
Trees infected by pine beetles

Evergreen Area Beetle and Forestry Facebook Page

Follow the page for local observations, photographs, educational information and discussions related to mountain pine beetle, Douglas-fir beetle and forest health in the Evergreen area. Social media information should be used as an educational starting point. Property-specific treatment decisions should be confirmed with a qualified forestry professional.
Jefferson County Colorado logo

Jefferson County Mountain Pine Beetle Resources

Jefferson County provides current beetle-flight information, identification guidance, treatment options, monthly homeowner tips, contractor information, mapping resources and updates about any available landowner-assistance programs.
Evergreen Fire Rescue logo

Evergreen Fire/Rescue

Evergreen Fire/Rescue provides local mountain pine beetle information, wildfire-preparedness resources and a community survey residents can use to report beetle impacts and support local mitigation planning.
Colorado State Forest Service logo

Colorado State Forest Service

The Colorado State Forest Service offers detailed identification photographs, management guidance, annual forest-health reports and separate resources for mountain pine beetle, Douglas-fir beetle and other insects affecting Colorado forests.