Innovative and sustainable control of bark beetles on spruce logs

European spruce bark beetle (Ips typographus) is one of the most damaging forest pests affecting Norway spruce (Picea abies) forests across Europe. Following large-scale disturbance events such as the Vaia windstorm of 2018, the availability of breeding material has contributed to increased bark beetle population growth, creating an urgent need for effective and sustainable timber protection strategies. This study evaluated the efficacy of conventional and bio-based treatments for reducing bark beetle colonization of freshly harvested Norway spruce timber under field conditions. Field experiments were conducted in 2025 within the framework of the Innovative Pest Sustainable Control to Reduce the Impact of Bark Beetle and Weevil Attacks on Alpine Forests (IPS) project and AGRIN field trials. Treatments included the synthetic insecticide Lanzarta® SYN and the bio-based formulations Microsap® Power Leaf and NA25_8. Individual log and operational log-pile experiments were assessed through photographic re-analysis of debarked bark sections. Colonization by Ips typographus, other bark beetles, and longhorn beetles was quantified using generalized linear mixed models and correlation analyses. In individual logs, treatments did not significantly affect I. typographus gallery abundance or colonized bark area. However, NA25_8 significantly reduced the abundance and colonized bark area of non-target bark beetles compared with untreated controls. In log piles, Lanzarta® SYN significantly reduced entrance hole abundance during the early stages of colonization, whereas Microsap® Power Leaf showed weaker and less consistent effects. Treatment differences were no longer significant at later assessment stages, and no significant effects on final gallery abundance or colonized bark area were detected.