RESPONSE ON THE GROUND OF BARK BEETLE AND WEEVIL SPECIES COLONIZING CONIFER STUMPS AND ROOTS TO TERPENES AND ETHANOL

Responses of three Hylastes species, Dryocoetes autographus, and two Hylobius species to terpenes and ethanol were studied in field experiments on clear-cut forest sites in Sweden using baited ground traps. Alpha-Pinene alone did not attract any of the six species. A terpene blend (spruce turpentine consisting mainly of alpha-pinene, beta-pinene, and 3-carene) attracted Hylastes cunicularius, H. brunneus, and Hylobius abietis in some experiments, but not in others. The attractiveness of ethanol also varied; the only species consistently attracted was H. abietis. Baits containing both terpenes and ethanol, particularly the combination of spruce turpentine and ethanol, were attractive to all species except Hylobius pinastri. In H. abietis, the terpene plus ethanol/ethanol catch ratios increased during early summer. Seasonal differences in catch levels were observed in H. cunicularius and H. abietis. The addition of alpha-pinene reduced the attractiveness of the combination of spruce turpentine and ethanol to H. cunicularius, H. opacus, and D. autographus. The differences in response to the volatiles between species are probably related to differences in reproductive behavior and host preferences.