Mountain pine beetle
Limber pine, Lodgepole pine, Ponderosa pine and Western white pine
Appearance and Life Cycle
Adult beetles are stout, black, cylindrical and approximately 6 millimetres (mm) long. They may be present from early July into September.
Unmated females make the initial attack on green trees and then release an odor which attracts males and other females. Adult females bore through the bark, then tunnel upwards. Mated females lay small, pearly-white eggs singly in niches along each side of the gallery. After hatching, yellowish-white, legless larvae tunnel galleries into the sapwood, at right angles to the main gallery. The larvae cease feeding in the fall, overwinter, and resume feeding in April. From late June to mid-July, larvae pupate and become adults. Mature adults may emerge directly or congregate under the bark and emerge from a common exit hole.
The mountain pine beetle is a destructive pest of pine forests, and although currently present in western Canada, the insect may become a threat to the prairie provinces in the future. The primary cause of death of host trees is larval feeding in the sapwood. The introduction of blue stain fungi and other microorganisms aids in the death of the trees. Pitch tubes consisting of a mixture of resin, wood borings and wood dust in bark crevices and around the base of the tree indicate the presence of beetles. Foliage of infested trees remains green until spring, then changes to greenish-yellow, then light orange and finally to rusty-brown by July.
Natural factors such as weather, woodpeckers, nematodes, insect predators and parasites do not keep outbreaks in check. Control methods such as felling and burning infested trees or treating with chemicals have been used, but are now considered uneconomical. Harvesting of infested or susceptible timber is possible, even though large areas must be covered in a short period of time.
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