Comparison of antennal responses of Ovalisia festiva and Phloeosinus aubei to volatile compounds of their common host, Thuja occidentalis

The cypress jewel beetle, Ovalisia festiva L. (Coleoptera: Buprestidae, Chrysochroinae), and the cypress bark beetle, Phloeosinus aubei Perris (Coleoptera: Curculionidae, Scolytinae), are invasive wood-boring pests of scale-leafed conifers (Cupressaceae), threatening tree nurseries and urban green areas. In order to reveal which volatile compounds of their common host, the American arborvitae, Thuja occidentalis L. cultivar 'Smaragd', they can perceive, we collected headspace volatiles from live attached twigs and screened them for bioactivity by gas chromatography coupled to an electroantennographic detector (GC-EAD). Compounds eliciting antennal responses were identified by gas chromatography coupled to mass spectroscopy (GC-MS). Synthetic samples of bioactive compounds were then screened by electroantennography. GC-EAD analyses of volatile collections revealed that E-beta-caryophyllene elicited antennal responses only from O. festiva (from both sexes), whereas borneol only from P. aubei. Electroantennography screening of synthetic compounds showed further differences between the two species. Even many of those compounds, which elicited responses from both species, differed in the relative intensities of responses they evoked. This indicates that O. festiva and P. aubei probably use different key compounds in the Thuja volatile blend for host recognition.