Mountain Pine Beetle

Adult mountain pine beetle, Dendroctonus ponderosae
© Canadian Forest Service

The mountain pine beetle is a naturally occurring insect of the Rocky Mountain ecosystem. These small cylindrical insects attack and kill mature trees by boring through the bark and mining the phloem - the layer between the bark and wood of the tree. When conditions are favourable, populations of the mountain pine beetle can increase and large numbers of trees can be infected, killing large areas of mature lodgepole pine.

This natural process is important to the forest ecosystem because, as a natural disturbance, it sets the stage for forest regeneration.

Life cycle of the mountain pine beetle

Mountain pine beetles normally have a one-year life cycle. In late summer, adults, which are approximately 5 mm (1/4") long, leave the infected trees in which they have developed. They then seek out living, green trees that they attack by tunneling under the bark and search for mates.

Tree stump showing blue stain fungi
© Canadian Forest Service

The beetles tunnel into the tree and lay eggs in vertical galleries under the bark. After the eggs hatch, the grub-like larvae spend the winter feeding under the bark. Larvae pupate in the spring and emerge as adults from July to September.

A key part of this cycle is the transmission of blue stain fungi from the beetle to the tree. Spores of these fungi are introduced by adults into the tree during colonization.

Fungi grow within the tree and, together with bark beetle feeding, weaken it. This mutual network of beetle galleries and blue stain fungi disrupts the movement of water within the tree and rapidly kills it. The fungi give a blue-grey appearance to the sapwood.

What to look for:

Trees killed by mountain pine beetle have red needles.
© Parks Canada

• red needles on the crowns of trees;
• eggs or larvae under the bark, or their galleries under the bark;
• "pitch tubes" - bubbles of resin on the trunk where beetles tunnel into the bark;
• "sawdust" at the base of a tree or in bark crevices;
• woodpecker activity, such as holes in the trunk and bark chips on the ground.

What is the history of mountain pine beetle in the mountain parks?

The MPB is present in all mountain national parks, but has only reached epidemic levels in Kootenay, Yoho and Waterton. In the 1940s, there was a major MPB outbreak in Kootenay National Park. 65,000 ha of pine forest were affected. A minor outbreak in Banff National Park affected 4000 ha. In the 1970s, a major Mountain Pine Beetle epidemic moved from the US Rocky Mountains into southeastern BC and southwestern Alberta, including Waterton Lakes National Park. Through the 1980s, the beetles moved through Kootenay National Park. A small outbreak occurred in southern Banff National Park in the early 1980s.

In 1997 the annual insect and disease survey found that beetles had dispersed across the Continental Divide into the Brewster Creek, Healy Creek and Bryant Creek drainages of Banff National Park. Since then, the beetle population has grown and migrated eastward into the warmer, drier forests of the Bow Valley, including areas outside Banff National Park.

What are we doing about mountain pine beetle?

Parks Canada's policy provides the following direction to Banff National Park:

1. Native insects and diseases are natural ecological processes that should be allowed to proceed without interference if possible.
2. Where insects or disease pose a serious threat to provincial lands, intervention may occur, provided that it is effective and does not damage the park ecosystem.

To achieve both of these objectives, Banff National Park has established two different areas where different strategies are applied:

• Long term management zone: Prescribed fire are lit to reduce the extent of MPB habitat, thus preventing a large build-up of the beetle population.
• Short term management zone: Beetle colonized are burned by prescribed fire, cut and removed, or cut and burned to slow the growth growth of the beetle population. Pheremone baiting is used to concentrate beetle colonization to known areas.

Mountain pine beetle control treatments

2009 update

Pheromone Bait

Natural Resource Canada’s Canadian Forest Service released its annual Forest Conditions report for Banff National Park. The report summarizes the findings from the past season’s aerial and ground surveys for forest insects and disease. The activity of mountain pine beetle in Banff National Park expanded in 2008 with over 7000 newly discoloured trees mapped throughout the park. Results from last season’s overwinter mortality surveys indicate that the success of mountain pine beetle populations is variable across the park with some populations continuing to thrive (e.g. in the Fairholme area) while others are in decline (e.g. in the Turbulent Creek area). The report also indicates that mountain pine beetle populations are experiencing multi-year life cycles and delayed flights to new host trees.

Parks Canada’s primary tool for the management of mountain pine beetle populations is prescribed fire, as it helps to manage for both current and future outbreaks while mimicking a natural ecosystem process. Prescribed fire helps to reduce the amount of susceptible mountain pine beetle habitat and promotes forest diversity, encouraging the growth of tree species not targeted by the mountain pine beetle (e.g. Douglas fir). Parks Canada will continue to work with federal, provincial and municipal governments as well as the forest industry in Alberta and British Columbia to manage mountain pine beetle populations for the future.

Summary

Mountain pine beetle is a dynamic ecological process that has both large scale ecological benefits within the park and the potential for large scale economic impacts on industrial forests. As such, it requires an adaptive management approach that integrates the objectives of many land managers and interest groups.