Dendroctonus pseudotsugae (Scolytidae)

Douglas-fir beetle

Adults:

Dendroctonus pseudotsugae, the Douglas-fir beetle, adults burrowing in phloem. Adults are similar in size to Dendroctonus ponderosae. Newly emerged D. pseudotsugae burrow in phloem while their new exoskeletons harden.


Larvae:

Dendroctonus pseudotsugae, the Douglas-fir beetle, larvae burrowing in galleries. Similar to Dendroctonus ponderosae. Larvae with the longest tunnels are the oldest. Thus the egg laying female excavated the ovipositional gallery (idicated by arrow) from the bottom to top.


Damage:

Dendroctonus pseudotsugae, bark galleries. The maximum length of parent galleries is about 50 cm with an average of 25 cm. Unsuccessful attacks may form pitch pockets in lumber. No pitch tube is formed but resin may exude from upper attacks. Fresh frass found in bark crevices indicates attack. Foliage turns colour about one year after attack. There is usually a one year life cycle. A mature gallery has artistic symmetry.


Principal Hosts:

Douglas-fir and occasionally western larch.

Economic Importance:

DFB is the most important bark beetle enemy of Douglas-fir throughout its range. This insect normally breeds in slash, windfall and diseased trees, but at times the DFB becomes epidemic and kills apparently healthy trees over extensive areas.

References and Links:

EAG: 491-498, 504-505; FC: 357.

For management information, see BC Forest Practices Code Bark Beetle Management Guidebook (1995).

For more general information, see HForest and JP17.

Bark Beetles in BC is the BC Ministry of Forests (provincial) bark beetle website, with updates on recent surveys.

Additional Images:

Douglas-fir beetle galleries Cerambycid larvae and bark beetles under Douglas-fir bark collected in the IDF. Close up view of Douglas-fir beetle eggs and L1 larvae.