Toward a more effective management of the pine shoot beetle, Tomicus destruens, by enhancing the attractant activity of its commercial kairomone: effect of phloem volatiles from fire-injured pines

Abstract The pine shoot beetle, Tomicus destruens (Woll.) (Coleoptera: Curculionidae: Scolytinae), represents a significant threat in the Mediterranean forests. The beetle attacks weakened or stressed pine trees, thereby increasing the degradation of the forest ecosystem after a drought or wildfires. A commercially available kairomone (CK) composed of α-pinene and ethanol is currently used for monitoring and mass trapping strategies, but its efficacy could be improved. The objective of this study was to compare and identify volatiles present in the phloem of fire-injured Pinus halepensis , both before and after being infested by T. destruens. Such volatiles, which can either be of new appearance or show an increased abundance when compared with healthy pines, could be evaluated as complements of CK to enhance its attractiveness. The volatiles showing a significantly higher relative abundance in pre- and post-infested fire-injured pines phloem and which are also commercially available were β-myrcene, estragole, p-cymen-8-ol, α-terpineol, p-cymene, and methyl eugenol. An initial field trial showed that the addition of estragole, p-cymene, or methyl eugenol to traps baited with CK significantly increased the number of T. destruens captured. Based on these results, a more in-depth study focused on these three compounds was performed in two additional field trials. The enhanced attractant effect of estragole or p-cymene on CK was not validated in the new field trials, but adding high emission rate lures of methyl eugenol to traps baited with CK significantly increased trap catches by 59% and 41% in autumn and spring trials, respectively. To the best of our knowledge, this is the first report of methyl eugenol as a kairomone for T. destruens ; its potential use in management of this pest is discussed.