Eastern larch beetle

Overview

• Native to North America.
• The beetle bores into and feeds on the inner bark and sapwood portions of the larch trunk.

Host Species

Eastern larch beetle attacks larch or tamarack (Larix) trees.

Characteristics and life cycle

• Mature adults are 4mm long, dark brown in colour with reddish-brown wing covers.
• Adults emerge from the bark in May and bore into the trunk of stressed trees to feed and lay eggs.
• Eggs develop into larvae within tunneled galleries under the bark.
• It takes about a month for the larvae to develop into pupae, which develop into adults and complete the first generation by the end of the second month.
• The eastern larch beetle can produce two complete generations every summer.
• The beetles over-winter as adults beneath the bark and remain sexually immature until spring.

Symptoms and damage

• From a distance, the most obvious evidence of infestation is yellowing foliage that is visible by late July or early August.
• Up close, small boring holes, which can be easily overlooked, indicate the presence of a bark beetle.
• An infestation can also be recognized by the presence of long flows of resin and dark brown dust on the trunk from the excavation of galleries.
• During severe attacks, the numerous galleries excavated under the bark can disrupt sap flow, girdling the tree and potentially leading to tree mortality.
• The beetles are frequently observed in areas previously infested by larch sawfly (Pristiphora erichsonii) or an abiotic or environmental disturbance.
• Portions of a forest stand may die following an eastern larch beetle outbreak.
• In urban settings, larch that have declining vigour are often subject to severe attacks by this beetle.

Control measures

Prompt removal of sick and dead trees, along with bark stripping, can help prevent larch beetle populations from increasing.