Mountain pine beetle (Dendroctonus ponderosae)

Last Review/Updated: February 6, 2008

The mountain pine beetle (Dendroctonus ponderosae Hopkins) is the most destructive pest of mature lodgepole pine forests in North America. It is a small bark beetle (4.0-7.5 mm in length) that introduces 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. Periodic outbreaks of this insect destroy the pine trees in millions of hectares of forest in British Columbia (BC) and western US.

The mountain pine beetle situation is being closely monitored in Alberta. Click here for the latest updates.

Primary Hosts and Distribution

  • Lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.)
  • Limber pine (Pinus flexilis James)

The mountain pine beetle is a temperate pine forest pest with a range extending from Mexico to central BC; the eastern edge of the beetle distribution lies along the southern Rockies near the Alberta-BC border where the effect of the maritime climate ends. Thus, the majority of lodgepole pine forests in BC and almost the entire lodgepole pine forests in Alberta is outside the normal range of mountain pine beetle distribution. Mature, large diameter pine stands along the eastern slopes of the Rockies are most vulnerable to mountain pine beetle attack. For current maps, click here.

Life Cycle

The mountain pine beetle normally has a one-year life cycle in Alberta. However, it may take two years to complete the life cycle in high elevation areas.

Larvae

About two weeks after oviposition, white, grub-like larvae with brown heads hatch and mine new horizontal galleries. There they overwinter, protected from the cold temperatures by the bark. The beetle spends the winter in the larval stage underneath the bark, resumes feeding in spring and grows up to 7 mm in length.

Pupae

By late June to early July the larvae finish pupating in oval-shaped chambers at the end of narrow tunnels (larval galleries) and become adult beetles.

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 releases a sex pheromone to attract males. Then, the females 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.

Detection and Damage

Look for the following signs and symptoms:

  • Cream coloured resin (pitch) oozing out of beetle entry holes (pitch tubes) on the tree trunk.
  • Boring sawdust found in bark crevices and around the base of the tree.
  • Egg galleries (J-shaped and up to 41 cm long) under the bark, beginning above the entrance holes and running along the grain of the wood.
  • Greyish blue sapwood caused by blue-stain fungi carried by the beetles.
  • Yellowish-green to reddish-brown needles throughout the crown of the attacked pine.
  • Woodpecker damage, often leaving a reddish appearance to tree trunks.

Death of high-value pines in thousands of hectares of forest is of prime concern during outbreaks. Mountain pine beetle reduces the aesthetic value of forests, the timber volume and the monetary gains of the high-value mature tree. The blue-stained wood lowers the commercial value of lumber. During the last mountain pine beetle outbreak (1977 to 1987) in Alberta, an estimated 1 068 167 m³ of lodgepole pine were killed (Brandt and Amirault, 1994).

Brandt, J.P.; Amirault, P. 1994. Forest insect- and disease- caused depletions to forests of west-central Canada: 1982-87. Nat. Resour. Can., Can. For. Serv., Northwest Reg., North. For. Cent., Edmonton, Alberta. Inf. Rep. NOR-X-333, p. 21).

It is important to note that the present lodgepole pine forest ecosystem in Alberta has evolved without the presence of the mountain pine beetle. Therefore, outbreaks of the mountain pine beetle may cause devastating impacts to the native fauna and flora, as well as affecting watersheds, soils and water quality.

Management

For the mountain pine beetle management strategy, click here. The mountain pine beetle management program in Alberta may include:

  • Annual aerial surveys used to spot areas infested in previous years. For more information, click here;
  • Ground surveys to detect current-year infested trees;
  • Using a 2-component pheromone bait to monitor for beetle presence. Baits are attached to trees in June and beetle attack is checked late in the summer. Infested trees are either removed (sanitation logging/burning) or debarked to destroy the population. For more information, click here;
  • Beetle-proofing highly susceptible pine stands by removing trees to adjust tree spacing to 4-5 metres apart, or commercially thinning stands to less than 750 trees/ha may help. However, beetle-proofing does not guarantee that the stand will not be attacked. During an outbreak, the mountain pine beetle prefers the nearest large diameter pine stand regardless of stand density;
  • Restricting pine log imports that have bark intact from infested areas to prevent infested logs from reaching Alberta during the period of beetle activity between June 1-September 30. For current restrictions, click here;
  • Detecting and destroying mountain pine beetle (MPB) infestations. The infested trees would be cut and burned, debarked or removed and processed before beetle emergence;
  • Focusing on "contain and control" if the beetles reach outbreak levels in spite of control efforts. This may include the use of pheromones to contain the beetle populations and sanitation cuts to remove infested trees.

Still want more information? Click here for the latest updates.