Response on the ground of bark beetle and weevil species colonizing conifer stumps and roots to terpenes and ethanol.

Responses of threeHylastes species,Dryocoetes autographus, and twoHylobius species to terpenes and ethanol were studied in field experiments on clear-cut forest sites in Sweden using baited ground traps.α-Pinene alone did not attract any of the six species. A terpene blend (spruce turpentine consisting mainly ofα-pinene,ß-pinene, and 3-carene) attractedHylastes cunicularius, H. brunneus, andHylobius abietis in some experiments, but not in others. The attractiveness of ethanol also varied; the only species consistently attracted wasH. abietis. Baits containing both terpenes and ethanol, particularly the combination of spruce turpentine and ethanol, were attractive to all species exceptHylobius pinastri. InH. abietis, the terpene plus ethanol/ ethanol catch ratios increased during early summer. Seasonal differences in catch levels were observed inH. cunicularius andH. abietis. The addition ofα-pinene reduced the attractiveness of the combination of spruce turpentine and ethanol toH. cunicularius, H. opacus, andD. autographus. The differences in response to the volatiles between species are probably related to differences in reproductive behavior and host preferences.

Mating stimulant of the pine weevilHylobius abietis (L.).

Factors eliciting copulatory behavior in mature maleHylobius abietis were studied in the laboratory. Dead female weevils were sexually attractive, while dead mature males and pentane-extracted female weevils were not. The sexual attractiveness of dead females declined with time after death. Pentane extracts of whole female weevils or of the anterior or posterior parts of their bodies elicited a copulatory response when applied to decoys. In contrast, extracts of hindgut or frass were inactive. Juvenile males were sexually attractive for about four weeks, after which their attractiveness gradually declined. The results indicate that the mating stimulant is present on the body surface of female and juvenile male weevils, and it can be extracted with pentane.

Methylbutynol effectively replaces methylbutenol, a pheromone component ofIps typographus (L.) (Coleoptera: Scolytidae).

In field experiments in Sweden, the constituent 2-methyl-3-buten-2-ol of the aggregation pheromone of the spruce bark bettleIps typographus (L.) was effectively replaced by 2-methyl-3-butyn-2-ol.

Gallery initiation byTomicus piniperda (Coleoptera: Scolytidae) on scots pine trees baited with host volatiles.

In a trapping experiment, wood chips from freshly cut Scots pine trees attracted flying adults of the bark beetleTomicus piniperda (L.) Healthy Scots pine trees, which usually are not attacked byT. piniperda, were baited with chips from freshly cut trees. In other experiments trees were baited with a mixture of (-)-α-pinene, (+)-3-carene, and terpinolene; the individual monoterpenes; or with ethanol alone. All baited treatments were attacked byT. piniperda. Most of the attacks resulted in short egg galleries and in larval galleries which were only a few millimeters in length. In trees from which a new generation of beetles emerged, net reproduction was well below 1.0. Unbaited control trees remained unattacked or received a few isolated attacks.