Great spruce bark beetle

Systematic position and distribution. The Great spruce bark beetle (Dendroctonus micans) belongs to the order Coleoptera, family Curculionidae, subfamily Scolytinae. It is a highly significant primary pest that can colonize healthy spruce trees, making it a major threat to coniferous forests across Eurasia and parts of the UK.

Host plants. The primary host is the Norway spruce (Picea abies), along with other spruce species like Sitka spruce. While it shows a strong preference for spruce, it may occasionally infest other conifers under specific conditions. Its ability to attack healthy, vigorous trees distinguishes it from many other secondary bark beetles that only attack already stressed or dying wood.

Biology and life cycle. The development of Dendroctonus micans depends heavily on regional climate, with a life cycle lasting between 1 to 3 years. Unlike other bark beetles that create individual galleries, the females lay eggs in a mass inside a common brood chamber. Larvae live and feed together in a group, excavating a large, shared area under the bark as they grow.

Damage and economic significance. Infestation is characterized by visible resin flow (resin tubes) on the trunk. The feeding activity of the larvae destroys the phloem and cambium, effectively girdling the tree. This disruption of nutrient transport leads to the chlorosis of needles, crown thinning, and eventually the death of the tree if the infestation is severe and persistent.

Control measures. Management strategies emphasize early detection and rapid removal of infested trees to stop the spread. Biological control has proven highly successful, particularly the introduction of the predatory beetle Rhizophagus grandis. This natural enemy follows the prey into the tunnels and feeds on the larvae, providing a sustainable solution for managing beetle populations.

• Sanitary logging of infested spruce trees.
• Monitoring via pheromone-based detection tools.
• Biological control through the release of Rhizophagus grandis.
• Maintaining healthy stand density to improve tree vigor.