Changing volatile profile of arborvitae, Thuja occidentalis, by drying up and infestation: selective olfactory cues for the cypress bark beetle, Phloeosinus aubei

Abstract

The cypress bark beetle, Phloeosinus aubei (Coleoptera, Curculionidae, Scolytinae) prefers to build breeding galleries in decaying host trees. However, volatile cues, specific to trees suffering from drought stress or earlier infestation have not yet been reported. This knowledge would actually be most useful, as this invasive, wood-boring species established huge populations across the temperate zone of Europe and became a key pest of ornamental trees of Cupressaceae in tree nurseries and urban green areas. In order to reveal key components in host volatiles of stressed trees, which are perceived by the pest volatile profiles of intact arborvitae, Thuja occidentalis ‘Smaragd’ were compared to those suffering from drought, and fresh infestation of P. aubei. Analyses of volatiles by gas chromatography coupled to an electroantennographic detector revealed substantial differences between healthy, drying up and infested trees. Structure elucidation of the major antennally active components revealed that α-thujone was the major component in volatiles of healthy trees, while volatiles of infested trees were dominated by α-pinene and α-thujene. Besides that, trace amounts of camphene, fenchene, as well as substantial amounts of b-pinene, myrcene, limonene and p-cymene were also found in volatiles collected from trunks, housing fresh nuptial chambers of P. aubei. Fenchone was present in each type of volatiles, however, only in low amounts. Further studies should be directed to reveal the behavioral role of these components, which could be helpful in developing kairomone-based techniques for monitoring the flight of the pest in stands of scale-leafed trees.