(-)-Germacrene D : Masking Substance of Attractants for the Cerambycid Beetle, Monochamus alternatus (HOPE)

Abstract

Oxygenated terpenes separated from healthy Pinus densiflora wood are attractive to the cerambycid beetle, Monochamus alternatus, while the healthy pine is unattractive to it. Thus, the attractiveness of the pines appears to be masked by an unknown substance occurring in the healthy pine. A key compound (-)-germacrene D, was isolated from the steam distillate of healthy pine leaves by reduced-pressure distillation, HPLC and TLC. In an olfactometer chamber, the oxygenated terpenes elicited flight response in the female beetle, but (-)-germacrene D in combined use diminished the attractiveness. The inhibitory activity was also confirmed in a linear tube olfactometer. The locomotory response of the female was released by a mixture of (+)-juniperol and (+)-pimaral-attractants isolated from the healthy pine. However, the female ceased her locomotory movements when (-)-germacrene D was added to the attractant odor. Therefore, (-)-germacrene D functioned as a ;masking substance, i.e., an agent inhibiting the locomotory movements toward the attractant source.