title: Mortality risk from entomopathogenic fungi affects oviposition behavior in the parasitoid wasp Trybliographa rapae.
abstract: Biological control of pests in agroecosystems could be enhanced by combining multiple natural enemies. However, this approach might also compromise the control efficacy through intraguild predation (IGP) among the natural enemies. Parasitoids may be able to avoid the risk of unidirectional IGP posed by entomopathogenic fungi through selective oviposition behavior during host foraging. Trybliographa rapae is a larval parasitoid of the cabbage root fly, Delia radicum. Here we evaluated the susceptibility of D. radicum and T. rapae to two species of generalist entomopathogenic fungi, Metarhizium brunneum isolate KVL 04-57 and Beauveria bassiana isolate KVL 03-90. Furthermore, T. rapae oviposition behavior was assessed in the presence of these entomopathogenic fungi either as infected hosts or as infective propagules in the environment. Both fungi were pathogenic to D. radicum larvae and T. rapae adults, but with variable virulence. When host patches were inoculated with M. brunneum conidia in a no-choice situation, more eggs were laid by T. rapae in hosts of those patches compared to control and B. bassiana treated patches. Females that later succumbed to mycosis from either fungus laid significantly more eggs than non-mycosed females, indicating that resources were allocated to increased oviposition due to perceived decreased life expectancy. When presented with a choice between healthy and fungal infected hosts, T. rapae females laid more eggs in healthy larvae than in M. brunneum infected larvae. This was less pronounced for B. bassiana. Based on our results we propose that T. rapae can perceive and react towards IGP risk posed by M. brunneum but not B. bassiana to the foraging female herself and her offspring. Thus, M. brunneum has the potential to be used for biological control against D. radicum with a limited risk to T. rapae populations.
authors.affiliation: Department of Plant Protection Biology, Integrated Plant Protection, Swedish University of Agricultural Sciences, Växtskyddsvägen 3, P.O. Box 102, SE-230 53 Alnarp, Sweden. Electronic address: Linda-Marie.Rannback@slu.se.
authors.forename: Linda-Marie
authors.initials: LM
authors.lastname: Rännbäck
authors.affiliation: Department of Plant Protection Biology, Integrated Plant Protection, Swedish University of Agricultural Sciences, Växtskyddsvägen 3, P.O. Box 102, SE-230 53 Alnarp, Sweden.
authors.forename: Belen
authors.initials: B
authors.lastname: Cotes
authors.affiliation: Department of Plant Protection Biology, Chemical Ecology, Swedish University of Agricultural Sciences, Växtskyddsvägen 3, P.O. Box 102, SE-230 53 Alnarp, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Anderson
authors.affiliation: Department of Plant Protection Biology, Integrated Plant Protection, Swedish University of Agricultural Sciences, Växtskyddsvägen 3, P.O. Box 102, SE-230 53 Alnarp, Sweden.
authors.forename: Birgitta
authors.initials: B
authors.lastname: Rämert
authors.affiliation: Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Copenhagen, Denmark.
authors.forename: Nicolai V
authors.initials: NV
authors.lastname: Meyling
mesh_terms: D000818:Animals; D052982:Beauveria / Q000502:physiology*; D005260:Female; D054884:Host-Pathogen Interactions; D007814:Larva / Q000382:microbiology / Q000502:physiology; D052981:Metarhizium / Q000502:physiology*; D010058:Oviposition; D014863:Wasps / Q000382:microbiology* / Q000502:physiology
keywords: Beauveria bassiana; Biological control; Delia radicum; Intraguild predation; Metarhizium brunneum