The best time to check for Mountain Pine Beetle (MPB) infestation is in winter. Check for “pitch tubes” on the trunks of your trees. The tree forms these tubes in its attempt to flush out the intrusive beetles. If you see some, use a hatchet to cut off a bark piece to see if the underneath wood is discolored bluish-gray. If so, the tree(s) need immediate removal. Leaving affected trees allows MPB to spread rapidly in the following spring to other pines on the property or neighboring yards. Once the trees are removed, it is imperative that Mountain Pine Beetle control starts the following spring to protect unaffected Pines in the yard.

mountain pine beetle damage

Quick Facts….

  • The beetle is native to Colorado.
  • Mountain Pine Beetles kill large numbers of trees annually during outbreaks.
  • They attack trees stressed by old age, crowding, poor growing conditions, drought, fire or mechanical damage, and root disease.
  • The best remedy is health trees, so thin susceptible stands leaving well-spaced, healthy trees.
  • Preventive sprays can protect green, unattacked trees.

– Colorado State Extension Service

Most Coloradans are familiar with the havoc the Mountain Pine Beetle, Dendroctonus ponderosae, wreaks on many pines species in the State. All it takes is a drive in the mountains with vistas of reddish-brown trees as far as the eye can see. Outbreaks affect wilderness areas, mountain subdivisions, and urban back yards. Sometimes landscape pines many miles from the mountains die from beetles imported in infested firewood. The insect targets Ponderosa, Lodgepole, Scotch, Limber, Bristlecone, and Pinyon pine trees growing in yards across the Denver area. Once infected, the tree is not salvageable, so prevention is the best tact. Homeowners concerned about their pines should contact Ross Tree to schedule an appointment. Please fill out this service request form or call 303-871-9121.

Life History and Habits

Mountain Pine Beetles have a one-year life cycle. In late summer, adults emerge and fly over to large diameter pine trees and mate. The fertilized females tunnel vertically into the bark to form an egg gallery and lay about 75 eggs. After the eggs hatch, the larvae tunnel away, creating a characteristic MPB feeding patterns under the bark. Their larvae survive the winter by producing glycerol that acts as an antifreeze. Once spring arrives, their tunneling girdles the tree turning its needles yellow to red. Adult beetles emergence in the late summer and the breeding cycles starts again. 

mountain pine beetle lifecycle

The characteristic blue stain of beetle-killed pine comes from a hitchhiking fungus with a symbiotic relationship with the beetle. The MPB carries the fungi into any tree they attack. Mass beetle emergence kills at least two, or more, trees the following year under epidemic conditions. During outbreaks, the beetles also attack small-diameter trees. Vulnerable trees usually are adjacent to or near previously killed trees.

Look for the following symptoms of an MPB attack:

  • Brown, white, or pink popcorn-shaped masses of resin on the trunk called “pitch tubes” mark Mountain Pine Beetles tunnels.
  • Woodpeckers tear off tree bark to gain access to beetles and their larvae, leaving bark flakes and debris on the ground below your tree.
  • Look for boring dust around the base of a tree.
  • Tree crowns turn yellowish or reddish after 8 to 10 months after being attacked.
  • Take a hatchet, remove the bark, and look for live larvae, pupae, and adults.
  • An affected cut-down tree will have blue-stained sapwood. 


How to Control Mountain Pine Beetles

During outbreaks, natural predators cannot keep the MPB in check, so the beetles spread. Hard freezes in early fall and early spring kill the larvae and pupae, respectively. Sustained temperatures of 30 degrees below zero for at least five days will kill beetle larvae in the middle of winter. Unfortunately, Colorado mountains have not experienced hard winters in decades, and biologists believe that mild winters between 1998 through 2010 allowed the beetle populations to explode.

Homeowners with acreage kill MPB by peeling away the bark on logs to expose the larvae to the elements, causing the larvae to dehydrate, starve and die. They can also burn or bury the logs on their land. Planting other trees increases diversity, and thinning makes yards more beetle resistant. Once the MPB larvae are active in a pine tree, there is no “cure.” These tree(s) need removal and chipped to kill any beetles that are still present.

Mountain Pine Beetle Treatment

Once the MPB larvae are active in a pine tree, there is no “cure.” These tree(s) need removal and chipped to kill any beetles that are still present. MPV treatments protect trees from becoming infected. These treatments kill the beetles as they fly to a tree to start the breeding cycle. So, the timing of the treatment is critical to its success. We apply the product in late spring or early summer, before emergence. The adult beetles die as they land on the trunk and begin to burrow into the tree. The application protects high-value yard pines for a year. If beetles are activity within several miles of the property, protecting these trees from beetle attack may be necessary each year.

mountain pine beetle control spraying

Ross Tree’s motto is “Integrity in Action,” which means we are committed to minimizing our impact on the environment when delivering tree services. With three Qualified Supervisors (QS) licensed by the Colorado Department of Agriculture to handle pesticide products, Ross Tree only uses the products necessary to treat your trees and nothing more. Please check out our handbook on Why Hire a Professional Tree Service Company?

Why Hire a Professional Tree Service Company to Control Mountain Pine Beetles?

  1. Treatment of an already affected tree is a waste of money.

     

  2. Under dry conditions, it is easy to misidentify MPB infestations because of the absence of pitch tubes. 

     

  3. Application timing is critical to get the best control result. 

     

  4. Be sure you are controlling the right beetle. It is not uncommon for Do-It-Yourselfers to confuse Ips and related beetles that emerge early in summer with the MPB.

     

  5. Proper coverage is imperative to get the best result. Professionals use the right equipment to spray high into trees and take the time to treat the entire circumference of the tree. Incomplete product coverage creates “windows” for beetle attacks.

     

  6. Quality Supervisors licensed by the State of Colorado understand the proper dosage and correctly mix the chemicals with the right amount of water. 

     

  7. Manufacturers guarantee stable chemical properties for at least two years. Spraying old product wastes money.

     

  8. Spraying trees before a rainstorm might wash off the control product and waste money. 

     

For more information about the benefits of hiring a professional, please check out our handbook on Why Hire a Professional Tree Service Company?

Homeowners with Ponderosa, Lodgepole, Scotch, Limber, Bristlecone, or Pinyon pine trees on their property need to be proactive to protect them against Mountain Pine Beetles. Ross Tree embraces the concept of Tree Canopy Management, which uses a holistic approach to create shade, maintain tree health, promote species diversity, and lower long term maintenance costs of yard trees. The following tree management practices protect green unaffected pine trees for one year.

  • Thinning out pine stands, so the remaining trees have room to grow healthy.
  • Remove old, dying, or stressed trees.
  • Spray only green trees that are not affected by the MPB.
  • Water trees during winter and summer droughts.


The average height of a Ponderosa and Lodgepole pines in Denver is between 40 to 120 feet. Most Do-It-Yourselfers do not have the equipment to treat these trees. If you need Mountain Pine Beetles treatment, please call Ross Tree. We are at your service.