Attraction of the bark beetle parasitoid Roptrocerus xylophagorum (Hymenoptera : Pteromalidae) to host-associated olfactory cues

Studies Mere conducted to identify host location cues used by Roptrocerus x ylophagorum (Ratzeburg), a larval/pupal parasitoid of bark beetles. In Y-tu be olfactometer bioassays, female R. xylophagorum were attracted to infeste d bark (i.e., phloem, cambium, and outer corky bark tissues) removed from b olts of loblolly pine, Pinus taeda L., colonized by the late instar larvae and pupae of the bark beetle Ips grandicollis Eichhoff (Coleoptera: Scolyti dae). In contrast, bark taken from recently cut, uninfested bolts interrupt ed attraction to infested bark when these were presented together. Larval a nd pupal hosts isolated from infested bark were not attractive to parasitoi ds, whereas frass removed from the larval mines in infested Lark was highly attractive. Bark from which hosts or both hosts and host frass were remove d remained highly attractive. Bark sandwiches (fresh bark with the exposed surface pressed to glass microscope slides) infested with either third-inst ar or adult female I, grandicollis were attractive to female parasitoids, w hereas bark sandwiches with only mechanical damage to the phloem tissue wer e unattractive. A steam distillate of bark infested with host lanae was att ractive to female R. xylophagorum, whereas a distillate of fresh pine resin was not attractive. Volatiles from the experimental baits were collected o n Porapak Q and analyzed by coupled gas chromatography-mass spectrometry. S everal compounds were identified that distinguished baits with biological a ctivity. These data show the importance of the complete host/plant complex for attraction of R. xylophagorum to its host's habitat and suggest a possi ble role for particular odors from uninfested host plant tissue in directin g foraging parasitoids away from locations with few or no hosts.