title: Response to host density by the parasitoid Dolichogenidea tasmanica (Hymenoptera: Braconidae) and the influence of grapevine variety.
abstract: Natural enemies that respond to prey in a density-dependent manner may be able to quickly suppress pest populations before they reach economically damaging levels. Although it is primarily the combination of a natural enemy's functional response and a population numerical response that will influence the maximum number of pests attacked, other factors may influence a density-dependent response. We conducted large-scale field experiments, both artificially inoculating grapevines with larvae and using naturally occurring populations, to quantify and characterize the response of a parasitoid, Dolichogenidea tasmanica (Cameron) (Hymenoptera: Braconidae) to different densities of its host, the pest of grapevines, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae). We showed that the response of D. tasmanica to the density of E. postvittana was inversely density-dependent, and that the degree of parasitism was consistently and significantly higher in the grape variety Cabernet Sauvignon compared with Chardonnay. While the significant effect of variety on the degree of parasitism may provide an option for increasing the parasitism of E. postvittana by D. tasmanica, it also highlights how differences in host plant can influence trophic interactions.
authors.affiliation: Centre for Evolutionary Biology and Biodiversity, School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, SA 5005, Australia.
authors.forename: C A
authors.initials: CA
authors.lastname: Paull
authors.affiliation: CSIRO Ecosystem Sciences, GPO Box 2583, Brisbane, QLD 4001, Australia.
authors.forename: N A
authors.initials: NA
authors.lastname: Schellhorn
authors.affiliation: Centre for Evolutionary Biology and Biodiversity, School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, SA 5005, Australia.
authors.forename: A D
authors.initials: AD
authors.lastname: Austin
mesh_terms: D000818:Animals; D006790:Host-Parasite Interactions / Q000502:physiology*; D007814:Larva / Q000502:physiology; D016015:Logistic Models; D011156:Population Density; D013021:South Australia; D013045:Species Specificity; D027843:Vitis / Q000235:genetics / Q000469:parasitology* / Q000502:physiology; D014863:Wasps / Q000502:physiology*