Dendroctonus rufipennis (Scolytidae)

spruce beetle


Adults:

Dendroctonus rufipennis, the spruce beetle, adults. Similar to Dendroctonus ponderosae. Elytra reddish-brown. Length is about 4 to 7 mm. Light brown elytra of beetle on right indicates that the beetle only recently emerged from pupa.


Larvae:

Dendroctonus rufipennis (the spruce beetle), galleries and larvae. Similar to Dendroctonus ponderosae. There is a sclerotized plate on the dorsal side of each of the last two abdominal segments.


Damage:

Dendroctonus rufipennis, galleries in bark. Maximum length of parent gallery is about 24 cm. There are no pitch tubes, attacks are indicated by the presence of loose frass in bark crevices. Foliage turns colour about 1.5 years after attack. There is commonly a two year life cycle. Early feeding by L1 larvae is often gregarious and larvae can be found in a single enlarged chamber. Gallery structure becomes indistinct when larvae have completed their feeding.

Life cycle normally takes two years. In very warm summers, larvae can complete their development, overwinter as adults and be ready to attack stressed trees or wind falls the following spring.


Principal Hosts:

Engelmann, white and Sitka spruce in the west. Other Picea spp. are attacked throughout their range in North America.

Economic Importance:

At low population levels this insect usually breeds in slash and windfall. Sporadic epidemics may decimate extensive stands of mature, living spruce following blowdown events and successive warm summers.

References and Links:

EAG: 491-498, 505-506; FC: 359.

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

For more general information, see HForest and JP17.

BC Ministry of Forests (provincial) bark beetle website, with updates on recent surveys.

(Aug 2004): Read an account of the spruce beetle outbreak in the Upper Bowron Valley in the late 1970's.

Additional Images:

fresh attack feeding in new gallery developing galleries, discolouration of cambium
pupae blue stain introduced into sapwood by beetles