Mountain pine beetle in Alberta

MPB are capable of attacking and killing all species of pine including:

• lodgepole
• jack
• ponderosa
• scots or scotch
• whitebark
• limber

The MPB kills pine trees by clogging and destroying the conductive tissue of the tree by introducing a blue-stain fungi when attacking the tree. Its larvae feed in the phloem of the tree. The action of blue-stain fungi and larval feeding can kill the tree within one month of the attack.

The MPB, or Dendroctonus ponderosae Hopkins, is a small bark beetle about 4 to 7.5 mm in length – about the size of a grain of rice. The MPB is the most destructive pest of mature pine forests in North America. When beetle populations are small, they prefer stressed, mature or over-mature (80-plus years) pine. As populations grow, any pine over 12.5 cm in diameter can be killed, even healthy trees.

MPB lifecycle – In Alberta, MPB normally has a one-year life cycle. In higher elevation areas though, it may take 2 years to complete their life cycle.

Adults – In mid-July to mid-August, the stout, black adults bore exit holes through the bark and fly to attack new trees. The female beetle releases an aggregate pheromone to initiate mass attack and to attract males. The females then begin to tunnel through the bark and make vertical egg galleries.

Eggs – In the galleries, females mate with males in mid-summer and lay eggs individually along the sides of the gallery. Female beetles will lay approximately 60 eggs.

Larvae – About 2 weeks after eggs are laid, white, grub-like larvae with brown heads hatch and mine horizontal galleries under the bark. Here they overwinter, protected from cold temperatures by the bark. The beetle spends the winter in the larval stage and resumes feeding in the spring. The larvae grow up to 7 mm in length. Mature larvae are the most cold-tolerant lifestage but 50% will die if under bark temperatures are lower than -37.5C. 

For more information, see MPB and Cold Temperatures – The facts.

Pupae – By late June to early July, the larvae create oval-shaped chambers at the end of the larval galleries. Here they develop into adult beetles.

Minimize risks

The following steps can be taken to minimize the risk of MPBs infesting pine trees on your property and to prevent further spread.

Monitor

MPBs fly and infest new pine trees in late summer and evidence of an infestation can be seen by fall. Trees respond to attack by producing resin (pitch) at the attack location. External evidence of an infestation will be pitch tubes and reddish sawdust around the base of the tree. Once a tree is infested with MPB the needles will turn dull green, then yellow and eventually turn red the following summer.

Maintain health

MPBs are more likely to attack older, stressed pine trees. These trees may have been topped, poorly pruned, injured, root damaged or are suffering from drought.

Remove trees

You may remove or thin pine stands on your property by removing trees so the crowns do not touch. You may also want to consider diversifying your tree types to include other species of trees and age classes.

Repellents

Note: Before engaging in these activities, you may choose to consult your local tree professional. These actions can be potentially dangerous and are not guaranteed.

Verbenone can be used to help prevent attacks on pine trees. Verbenone is a naturally occurring chemical that mimics the scent beetles emit when a tree is heavily infested – this tricks beetles into believing the tree is occupied. The chemical can cause MPB to avoid attacking pine trees. Verbenone is specific to MPB and is not a pesticide. This tool is most effective when used to protect high value susceptible pine trees over a relatively small area when beetle populations are low.

The Verbenone Use Guidelines provide information to landowners, municipalities and forest managers on using verbenone for protection.

Disposal of infested trees

If a tree has fewer than 40 signs of MPB attack, the tree may survive by killing the beetles with pitch.

If you have a tree with 40 or more signs of MPB attack on your property you can control the beetles during the winter by peeling the bark off the tree and exposing the larvae to the cold or felling the tree and burning, chipping or burying it. It is important to do this before June the year following attack, or the beetles will mature under the bark and emerge to attack new trees.

It is important to remove the bark of infested trees before transporting to other locations to prevent spreading MPB. The transport of logs and other forest products cut from coniferous trees is regulated under provincial legislation. You can read the legal foundation for the management of public forests in Alberta at Forest directives and standard operating procedures.

Provincial MPB maps

• MPB Management Zones
• Pine Stands Affected by Mountain Pine Beetle in Alberta
• Mountain Pine Beetle Red Tree Density
• Mountain pine beetle Aerial Survey (Heli-GPS)
• Predicted overwinter MPB mortality

In 2007, Alberta’s MPB management program implemented both a strategy to manage MPB infestation and protect the health of our forests. The program employed a short-term, beetle-focused strategy and a long-term, pine-focused strategy. The short-term strategy consisted of direct population management through single tree control treatments. The long-term strategy focused on the reduction of MPB habitat by changing the amount and distribution of mature pine across the landscape through targeted harvesting.

These management actions have contributed to slowing the spread of MPB further into our pine forests, particularly throughout the watersheds of the eastern slopes and further into the boreal forest. Management actions, along with temperatures unfavourable for beetle development and survival, have resulted in a 98% decline in MPB populations throughout Alberta between 2019 and 2023. The province will continue to monitor the endemic populations of MPB that exist in Alberta’s forests.