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Mountain Pine Beetle

Dendroctonus ponderosae
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What is Ontario Doing?

To prevent this unwanted invader from coming into the province, Ontario has regulated mountain pine beetle as prohibited under the Invasive Species Act, 2015 . For more information on the Invasive Species Act and Regulations, visit


Mountain pine beetle is an insect responsible for creating widespread pine mortality in British Columbia. Native to western North American forests, this small beetle has reduced the growth of millions of trees and caused widespread mortality to commercial tree species. In the most recent infestation, estimated mortality from mountain pine beetle has reached into the hundreds of millions of trees and covers an area roughly five times the size of Vancouver Island.

Mountain pine beetle adults will tunnel into a tree where they lay their eggs. The small beetles will mass together and attack a tree as one coordinated force, overcoming the tree’s defenses and ability to “pitch out” the attacking beetles. Beetle larvae will then spend the winter feeding under the bark where they feed on the tree’s circulatory system. Between July and September, adult beetles emerge from the bark and fly in search of a new host tree.


The home range of the mountain pine beetle follows the west coast of North America from British Columbia and western Alberta to northern Mexico. The most extensive outbreaks have been in southern British Columbia and in the northern Rocky Mountains. Currently there are no populations in Ontario, however reports have predicted that climate change may allow the beetles to spread north and east.

Impacts of Mountain Pine Beetle

  • Widespread mortality of lodgepole pine (Pinus contorta) and commercial tree species such as sugar pine (Pinus lambertiana), western white pine (Pinus monticola) and ponderosa pine (Pinus ponderosa).
  • Increased risk of large fires with dead and dying trees creating a landscape of highly flammable stems.
  • Loss of wildlife habitat.
  • Degrades the overall visual quality of forests.

How to Identify Mountain Pine Beetle

  • Adult beetles are about 5 mm long and begin as a light creamy tan color, turning black when they mature.
  • Infected trees have red needles at the crown.
  • Sawdust collects at the base of infected trees from larvae feeding.
  • Larvae are legless grubs with red-brown heads and are found under the bark.
  • Beetles transfer a fungus to the tree that stains the sapwood blue.

What You Can Do

  • Learn how to identify mountain pine beetle and what infested trees look like, as well as which host trees they target.
  • Don’t move firewood or other potentially infested wood material over long distances. With firewood, remember: burn it where you buy it!
  • If you’ve seen a Mountain Pine Beetle or any other invasive species in the wild, please contact the toll-free Invading Species Hotline at 1-800-563-7711, visit EDDMapS  to report a sighting.

Resource Files


OFAH/OMNRF Invading Species Awareness Program. (2021). Mountain Pine Beetle. Retrieved from:
This factsheet may be reproduced for non-commercial purposes.

Header photo by Whitney Cranshaw – Colorado State University.

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