« Back

Tetropium fuscum

Brown spruce longhorn beetle

Description

Tetropium fuscum, known as the brown spruce longhorn beetle, is a species of longhorn beetle that primarily infests spruce trees (Picea spp.), including Norway spruce (Picea abies), but can also develop on other conifers like pine (Pinus spp.). It is native to Europe and parts of Asia, widely distributed in countries such as Austria, Germany, Russia, and across Scandinavia. The beetle has one generation per year, with larvae developing under the bark of weakened, dying, or recently felled trees. Adults emerge from June to July and are active during twilight and night, often found on freshly felled logs.

The larvae feed on the phloem and outer sapwood, creating galleries that disrupt nutrient transport within the tree. While they primarily attack stressed or dying trees, a high abundance can contribute to tree mortality and reduce the commercial value of timber by introducing fungal infections causing blue stain. Repeated infestations may worsen the overall health status of affected forests. Rare species.

Symptom

Under the bark, flat galleries filled with frass are present. Exit holes are oval-shaped, and resin may exude. Infested trees may show yellowing or thinning crowns.

Tree Species: Pine, Spruce

Part of a plant- attacked: Tree trunk, Branch

Pest significance: Harmful

Invasive Species: No

Present in EU: Yes