Evaluation of the efficiency of tree injection of Norway spruce against the European spruce bark beetle (Ips typographus) (Coleoptera: Scolytinae).

BACKGROUND: Ips typographus is the most important pest of Norway spruce (Picea abies), responsible for large-scale outbreaks in Central Europe that have led to extensive mortality of spruce stands. Control strategies rely primarily on timely sanitary felling, while other methods, including tree injection, play only a supplementary role. RESULTS: In 2022 and 2023, the efficacy of tree injection with emamectin benzoate was evaluated on Norway spruce. At each of 10 study sites, five trees were injected with 4 mL of 4.5% solution per hole drilled and five control trees were selected. All trees were baited with a pheromone lure to attract I. typographus. Following infestation, trees were debarked at seven sections distributed along the length of the main trunk to record the number and lengths of maternal and larval galleries. While the number of maternal galleries did not significantly differ between treated and control trees, the number of larval galleries was significantly lower in injected trees, suggesting that larvae of I. typographus are more sensitive to the insecticide than adults. Additionally, both maternal and larval galleries were significantly shorter in treated trees compared to control trees. The lengths of galleries, both maternal and larval, decreased progressively toward the top of the tree starting from the third section. CONCLUSION: The findings of this study suggest that emamectin benzoate injections could be a valuable tool for suppressing the development of I. typographus in Norway spruce. Injected trees can be a more environmentally friendly alternative method to insecticide-treated trap trees. However, further research is required to optimize application protocols and evaluate their long-term efficacy.