Emission Dynamics of Constitutive and Herbivore-induced Plant Volatiles from Norway Maple (Acer platanoides) Trunk Infested by the Asian Longhorned Beetle (Anoplophora glabripennis (Motschulsky))

Early detection of the Asian longhorned beetle (Anoplophora glabripennis, ALB), a destructive wood-boring pest, remains challenging in living trees. Volatile organic compounds (VOCs) have gained increasing attention as potential detection cues due to their key roles in plant-insect interactions, yet trunk-based volatile responses to wood-boring herbivores are still poorly understood. Here, we present a detailed case study characterizing constitutive and herbivore-induced plant volatiles (HIPVs) emitted from a living Acer platanoides trunk infested by ALB. Over six months, trunk emissions were monitored and analyzed noninvasively using thermal desorption gas chromatography mass spectrometry (TD-GC-MS). Constitutive emissions were dominated by aldehydes and were primarily influenced by abiotic factors such as temperature and light, whereas ALB infestation had only minor effects on their emission rates. In contrast, HIPVs were characterized mainly by terpenoids and exhibited infestation-stage-specific dynamics: monoterpenoids - dominated by p-cymene, (E)-4,8-dimethylnona-1,3,7-triene, and γ-terpinene - prevailed during oviposition, whereas sesquiterpenoids dominated during larval feeding, particularly cyclosativene, α-longipinene, α-copaene, zingiberene, and α-curcumene. In addition, nitrogen- and oxygen-containing volatiles were identified as previously unreported components of the ALB-induced trunk volatile blend. Several induced terpenoids are known to elicit electrophysiological or behavioral responses in ALB and its natural enemies, and therefore represent valuable key compounds that can be utilized for olfactory detection purposes. Though requiring validation with replications and analogous experiments with further plant and insect species, the findings of this study provide valuable mechanistic insights in tritrophic interactions between plant, wood-boring insect and its enemies.