Olean (1,7-dioxaspiro[5.5]undecane): A Novel Intraspecific Chemical Cue in Coraebus undatus (F.) (Coleoptera: Buprestidae)

Simple Summary: The flathead oak borer Coraebus undatus (F.) (Coleoptera: Buprestidae) is a major pest of cork oak (Quercus suber) along the Mediterranean Basin that generates significant economic losses in the cork industry. Larvae bore long galleries and feed on the cork generating layer, thus affecting its quality. At present, the semiochemistry of this species is poorly known, and therefore the elucidation of chemicals involved in its intraspecific communication may allow the development of novel control tools. We determined that both sexes release the compound 1,7-dioxaspiro[5.5]undecane, and the biological activity of the compound was addressed by means of electroantennography and behavioral assays. The attractiveness of the compound on both sexes under laboratory conditions contrasts to its performance in field trials, which may be explained by features inherent to the methodological design (e.g., the absence of a contextually related visual stimulus or trap deployment height). This is the first time in which an intraspecific compound has been reported as attractive for the species, and practical implications for the assessment of its activity under natural conditions are also further discussed.The main aim of this work was to identify semiochemicals from the jewel beetle Coraebus undatus (F.) (Coleoptera: Buprestidae) that may aid in the improvement of current monitoring tools. First, HS-SPME collections revealed that individually sampled adults (> 7 days old) of both sexes release the spiroacetal 1,7-dioxaspiro[5.5]undecane (olean). Electroantennographic recordings from both sexes exposed to increasing amounts of olean followed a dose-dependent pattern, with females being more responsive than males to the highest amount of the compound (100 mu g). In double-choice assays, adults older than seven days were significantly attracted to olean, whereas this attraction was not detected in insects aged less than seven days. Indeed, a repellent effect was observed in young females. Subsequent field trials employing sticky purple prism traps revealed that there were no differences among the number of insects caught in control and olean-baited traps at two different release rates (0.75 and 3.75 mg/day). Interestingly, all the trapped specimens were determined as mated females, regardless of the presence of olean. Overall, these findings provide a basis for unraveling the chemical ecology of the species, although further research is still needed to determine the specific role of this compound within the chemical communication of the species.