Mountain pine beetles attack and kill mature pine trees. Pines larger than 20 cm in diameter (measured 1.4 metres off the ground) are the size preferred by beetles. When beetle populations are low, they prefer stressed, over-mature trees. As beetle populations increase, pine over 12.5 cm in diameter may be killed – even healthy trees.

All species of pine are vulnerable to attack, including the 4 species native to Alberta- lodgepole, jack, whitebark, and limber, as well as the hardy introduced species often planted in shelterbelts and yards- ponderosa, Scots, red, Austrian, and eastern white pine. Mountain pine beetles do not attack spruce or fir trees.

On the main trunk, look for soft, creamy globs of resin that look like crystallized honey, called pitch tubes, and sawdust at the base of the tree and in bark crevices.

Beetles fly in search of new trees in July and August. The female beetle releases an aggregate pheromone to initiate a mass attack and to attract males. The females then begin to tunnel through the bark and lay eggs. The cycle of eggs hatching and maturing to become beetles is normally one year in Alberta.

The action of females constructing galleries under the bark for egg laying and the feeding of the larvae interferes with water and nutrient movement in the tree. As well, the beetles introduce a blue stain fungus that grows and interrupts the flow of water to the top of the tree.

Healthy trees can resist attack by producing resin to expel beetles. Natural enemies, including disease and predators, along with cold weather can also kill beetles and prevent tree death. Generally, healthy trees can withstand more than 100 hits/tree (identified by the cream-coloured pitch tubes) and are able to survive an attack. These trees may not need to be removed.

Trees overwhelmed by mountain pine beetles usually die within one year. Before making the decision to remove a tree, homeowners can monitor it for signs of a successful attack. In May and June of the year following an attack, look under the bark for live larvae and their feeding galleries.  Starting above a pitch tube, use a hatchet to gently peel back the bark. From May to early July, the year after the attack, affected trees will begin to turn a pale green, looking noticeably different than healthy pine trees.

Scout out the pine trees on your property and identify trees that have been successfully attacked. Falling and burning is the usual strategy for removing a small number of trees.  This involves felling, bucking, piling, and burning infested portions of the tree. Another option is to hire an arborist to fall and chip the infested wood, this can be left on site. This work should be done before July when the developing beetles could emerge to attack nearby trees. MPB-infested pine firewood must not be transported if the bark is attached.

Scout out the pine trees on your property and identify trees that have been successfully attacked. Falling and burning is the usual strategy for removing a small number of trees.  This involves felling, bucking, piling, and burning infested portions of the tree. Another option is to hire an arborist to fall and chip the infested wood, this can be left on site. This work should be done before July when the developing beetles could emerge to attack nearby trees. MPB-infested pine firewood must not be transported if the bark is attached.

Our Agricultural Services staff can assist with identification of mountain pine beetle and recommending control measures. Early detection and control by residents play an important role in managing Alberta’s MPB infestation and preventing further spread.