Impacts of the pest wood-boring beetle, Eupromus ruber, on Lauraceae species in temperate coastal forests

Context : Lauraceae species have become key components of temperate coastal forests, particularly following the decline of pine trees. The wood-boring beetle Eupromus ruber , known to infest Lauraceae, is expanding its distribution in these forests, potentially impacting tree health and forest ecosystems. Aims : This study aims to investigate the invasion of E. ruber , identify preferred Lauraceae host trees, and evaluate whether oviposition and larval boring increase the risk of stem breakage in temperate coastal forests. Methods: Field surveys were conducted in coastal forests to assess the extent of damage caused by E. ruber on its host tree, Machilus thunbergii . The number of oviposition scars and stem breakage were recorded for individual trees. Generalized linear models (GLMs) were used to evaluate environmental factors affecting E. ruber activity and the association of E. ruber with stem breakage in its host. Results : GLM analysis revealed a positive correlation between the number of oviposition scars and both tree height and relative photosynthetic photon flux density (rPPFD), indicating that E. ruber preferentially oviposits on taller, sun-exposed M. thunbergii trees. Stem breakage was associated with the presence of oviposition and larval boring, suggesting that E. ruber activity increases the risk of stem failure in its host. Conclusion E. ruber infestation weakens M. thunbergii stems, increasing breakage risk in snowy coastal forests. Monitoring and integrated management are crucial for maintaining forest stability.