Spruce Beetle

The spruce beetle (Dendroctonus rufipennis) is a species of bark beetle native to British Columbia. It destroys forests of spruce trees by consuming the phloem of Englemann, white, Sitka and Colorado blue spruce. Adults are tiny, averaging four to seven millimetres in length (about half a centimetre).

Though the spruce beetle tends to infest recent blowdown and freshly-cut logs, outbreaks have been devastating to living white and Engelmann spruces throughout western North America. It's the most damaging pest of mature and overmature Interior spruce in B.C. Outbreaks prior to 2000 resulted in losses of three billion board feet from B.C.'s forests.

Description

Adults are hard, stout-bodied cylindrical insects, with black-brown or black reddish wing covers. Spruce beetles must overwinter once to mature fully. Mature adults emerge and attack fresh host material from late May to early July. Some immature adults may emerge in the fall to overwinter at the base of the tree.

The spruce beetle has a one- to three-year life cycle — usually two years. Its flight and attack period starts in June or soon after most of the snow around the trees has melted. It bores 12.5-cm long galleries in the  inner bark, and lays three to four groups of eggs alongside the galleries, about 100 eggs per gallery. The larvae feed in the phloem, usually gregariously, often forming fan-shaped galleries. When a one-year cycle occurs due to favourable weather, beetle flight numbers can double.

Managing the Spruce Beetle

Selecting an appropriate management strategy for a spruce beetle infestation will depend on proper detection and a number of site-specific factors.

The guidebook Spruce Beetle Management in B.C. and its related technical documents offer full details on hazard rating, risk rating, ground detection, prevention, and management options.

Current Activity

The following factsheet includes current information on spruce beetle activity in North-Central B.C.:

Images of the Spruce Beetle & Its Damage

Woodpecker bark-scaling of an attacked tree.
Woodpecker bark scaling of an attacked tree.

Adult spruce beetle (fig. 65)
Adult spruce beetle.

Trees fade to yellowish-green and then grey within a year following an attack (fig. 66)
Trees fade to yellowish-green and then grey within a year following an attack.

Egg and larval galleries are up to 13 cm long. Frass is usually present in the galleries (fig 67)
Egg and larval galleries are up to 13 cm long. Frass is usually present in the galleries.

 

Larvae. Note the anal shields (fig. 68)
Larvae. Note the anal shields.