Host selection and structural consequences of Eupromus ruber (Dalman, 1817) (Coleoptera: Cerambycidae) in Lauraceae-dominated coastal forests

Abstract Key Message In temperate coastal forests in Japan, Lauraceae species, particularly Machilus thunbergii Siebold & Zucc. and Neolitsea sericea (Blume) Koidz., are commonly planted following pine decline. In a temperate coastal forest, Eupromus ruber (Dalman, 1817) preferentially oviposited on M. thunbergii , and oviposition on the bole increased the risk of breakage. These findings highlight the need for monitoring and integrated pest management in Lauraceae-dominated coastal forests to mitigate bole damage and maintain forest functions. Context Lauraceae species have become key components of temperate coastal forests following the decline of pine trees, particularly in areas affected by pine wilt and other disturbances. The wood-boring beetle E. ruber , which primarily infests Lauraceae, occurs on these trees and may influence the health and bole stability of its hosts. Aims This study aims to assess the occurrence of E. ruber in temperate coastal forests exhibiting Lauraceae species succession, evaluate host use among dominant Lauraceae tree species, and determine whether oviposition and larval boring in M. thunbergii increase the risk of bole breakage. Methods Field surveys were conducted in coastal forests to assess the extent of damage caused by E. ruber on its host tree, M. thunbergii . The number of oviposition scars and bole 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 bole breakage in its preferred host, M. thunbergii . 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. Bole breakage was associated with the presence of oviposition and larval boring, suggesting that E. ruber activity increases the risk of bole failure in its host. Conclusion Damage was observed primarily on M. thunbergii , whereas no damage was detected on the surveyed N. sericea trees. M. thunbergii infestation significantly increased the risk of bole breakage.