Thuja occidentalis: identification of volatiles and electroantennographic response by the invasive cedar bark beetle, Phloeosinus aubei

Abstract

Recently, the distribution of the Mediterranean cedar bark beetle, Phloeosinus aubei Perris (Coleoptera: Scolytidae), has expanded to Central Europe. Reported mostly on cypress in the Mediterranean area, potential host plants in the invaded range include other scale-leafed conifers, such as cultivars of arborvitae, Thuja occidentalis L. To reveal potential kairomonal cues for P. aubei, volatiles of T. occidentalis were collected and analysed by gas chromatography with electroantennographic detection (GC-EAD). Assignments of chemical structures of antennally active components were carried out by gas chromatography linked to mass spectrometry (GC-MS) using authentic reference samples. Antennal responses to synthetic samples of the identified compounds were studied by electroantennography (EAG), with antennae of female and male P. aubei. GC-EAD analysis of head space volatiles of T. occidentalis revealed 22 antennally active compounds, of which 21 were identified. The most abundant components were a-and bthujone, fenchone, camphor, terpinen-4-ol, bornyl acetate and a-terpinyl acetate, all of which are oxygenated monoterpenes. When EAG activities of synthetic samples were compared, the most intensive responses from female antennae were elicited by a mixture of a-and b-thujone, followed by (-)-terpinen-4-ol, (+)-camphor, cis-4-thujanol, (+)-sabina ketone, (+)-terpinen-4-ol, isopulegone, (-)-fenchone, borneol, (3Z)-hexen-1-ol, (-)-1-octen-3-ol and (+)-sulcatol. Male antennae responded the most to (-)-terpinen-4-ol and cis-4-thujanol followed by the mixture of a-and b-thujone. The next highest responses were elicited by (+)-camphor, borneol, (+)-terpinen-4-ol, (+)-sulcatol and (+)-sabina ketone. Striking differences were found between responses to the enantiomers of fenchone, sulcatol and 1-octen-3-ol, whereas responses to the enantiomers of terpinen-4-ol did not differ significantly from each other. Several antennally active volatiles of T. occidentalis have also been reported from cypress and various other members of the Cupressaceae, suggesting that the sensory apparatus of P. aubei may recognize the shared components, which may enable rapid adaptation to new hosts in the invaded areas.

Occurrence of the Invasive Bark Beetle Phloeosinus aubei on Common Juniper Trees in the Czech Republic

“…The monitoring of invasive bark beetle is necessary [79]. The use of pheromone trapping for monitoring P. aubei is not currently possible, because P. aubei pheromones have yet to be identified [23]. At present, P. aubei populations can be monitored by the debarking of symptomatic juniper and thuja trees in the field.…”

“…In the 1980s, the northern edge of the P. aubei range was in Central Europe, i.e., in northern Austria, southern Moravia (Czech Republic), southern Slovakia, and southwestern Hungary [7,9,17,22,23]. This invasive beetle was subsequently detected further north, i.e., in Brandenburg in 2001 [22,24], in the Netherlands in 2004 [25], in eastern Slovakia in 2007 [26], and in Poland in 2014 [20].…”

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

“…X denotes that retention time to that particular compound in the volatile collection matched to that of the synthetic standard. Compounds marked by # were already reported in Bozsik et al (2016).…”

“…P. aubei was shown to perceive T. occidentalis ‘Smaragd’ volatiles, as revealed by analysing T. occidentalis ‘Smaragd’ volatile collections by gas chromatography linked to an electroantennographic detector (GC‐EAD), corroborated by electroantennographic measurements of selected synthetic headspace compounds (Bozsik et al, 2016). By contrast, no information is available on which compounds of the host plant headspace are perceived by O. festiva .…”

Bionomics and host plants of the invasive Cydia interscindana (Möschler, 1866) (Lepidoptera, Tortricidae), an emerging pest in the Carpathian Lowlands

“…1864 are popular evergreens used as ornamental trees both in parks and gardens. In Hungary several pests of these plants have been recorded, all probably introduced with imported plants; in the literature, 11 Lepidoptera, nine Coleoptera and six Hemiptera species have been mentioned already (Csóka and Kovács 1999;Maráczi 2013;Bozsik et al 2016;Schurov et al 2017). However, until the end of the 2000s, only Scolytidae (Coleoptera) species caused serious damage (Bozsik and Szőcs 2017).…”