Spruce beetles (Dendroctonus rufipennis (Kirby)) occur in endemic populations in white spruce stands throughout Alberta. Outbreaks of the spruce beetle often originate from areas with blowdown, logging slash, or damaged standing timber. Spruce beetles breed in these areas and may attack and kill healthy trees.
Primary Hosts and Distribution White spruce (Picea glauca (Moench) Voss) Engelmann spruce (P. engelmannii Parry). Spruce beetle is common throughout Alberta, especially in areas with abundant mature spruce trees.
The spruce beetle usually has a 2-year life cycle in Alberta.
Adults Stout dark brown adults (about 4.5-7.0 mm long) overwinter in the tree, then emerge and attack new hosts from late May through June. The female beetle tunnels egg galleries along the wood grain in logs, stumps or standing trees. The female beetle mates with a male in the gallery and then lays eggs.
Eggs The female lays white eggs along the gallery walls.
Larvae and Pupae
The eggs hatch in 2 to 4 weeks and the young larvae tunnel under the bark away from the gallery. The larvae are white grubs with brown heads and are about 3-7 mm long. In the 2-year life cycle, spruce beetles overwinter as larvae. By the following summer the larvae pupate and become adult beetles. In late summer, the adults come out of the galleries, and reenter the tree at the base and spend the final winter there.
Detection and Damage Look for the following signs and symptoms:
Entrance holes bored into the bark of the lower stem in late May and June.
Boring dust and resin (pitch tubes) on the tree trunk, and boring dust at the tree base.
Straight egg galleries (6-23 cm long) under bark that follow the wood grain.
Woodpecker predation, leaving a reddish tree trunk.
Yellowish-green to reddish colored needles throughout the crown.
The spruce beetle can seriously damage large-diameter spruce during outbreaks, which can last 2-5 years. Larval feeding within the bark can lead to colonization of blue stain fungi and other associated fungi. Fungi disrupt the water transportation within the tree and kill the tree.
Management For more information about aerial or ground survey standards, data or initiatives, click here. In Alberta, the spruce beetle management program can include:
Aerial surveys, especially of mature spruce stands that surround an outbreak, blowdown areas or storm-damaged stands;
Using Lindgren® funnel traps baited with pheromones (3-component lures) during the summer, if necessary to predict the population trends;
Ground surveys to detect and assess current year infestations;
Felling beetle-susceptible healthy trees (trap logs) to trap beetles in outbreak areas before spring. After beetle attack, trees are removed from the area and processed before the beetle completes its development;
Sanitation logging of infested stands. Infested trees are cut and processed quickly or if required, burned before the beetles emerge.