Small spruce bark beetle

Systematic position. The small spruce bark beetle (Latin Polygraphus subopacus) belongs to the order Coleoptera and the family Curculionidae, specifically the subfamily Scolytinae. It is a specialized insect pest known for inhabiting the bark and phloem of coniferous trees, particularly in Northern and Central Europe.

Host plants. The primary host for this species is the Norway spruce (Picea abies). While the beetle often acts as a secondary pest attacking trees stressed by drought, windthrow, or fungal diseases, in high-density populations, it can also infest trees that appear relatively healthy, contributing to rapid stand degradation.

Biology and life cycle. The life cycle involves overwintering as adults or larvae beneath the bark. In the spring, when temperatures rise, the beetles emerge for maturation feeding and subsequent mating. Females construct brood galleries in the phloem where they lay eggs, and the emerging larvae feed by creating individual mines radiating from the main gallery.

Damage and harmfulness. The feeding activity of larvae and adults disrupts the flow of nutrients in the cambium layer. This mechanical injury effectively girdles the tree, causing the crown to lose color and eventually turn reddish-brown. If the infestation is widespread, the structural integrity of the tree is compromised, leading to economic losses in forestry.

Protection measures. Integrated pest management (IPM) is essential for controlling this beetle. Key strategies include:

• Prompt removal of infested trees (sanitary thinning) before the next brood emerges;
• Use of trap logs to attract and collect beetle populations during the flight period;
• Monitoring programs using pheromone traps to assess population density;
• Maintaining forest hygiene by removing logging residues and fallen timber where beetles could potentially breed.