title: Powdery mildew suppresses herbivore-induced plant volatiles and interferes with parasitoid attraction in Brassica rapa.
abstract: The co-occurrence of different antagonists on a plant can greatly affect infochemicals with ecological consequences for higher trophic levels. Here we investigated how the presence of a plant pathogen, the powdery mildew Erysiphe cruciferarum, on Brassica rapa affects (1) plant volatiles emitted in response to damage by a specialist herbivore, Pieris brassicae; (2) the attraction of the parasitic wasp Cotesia glomerata and (3) the performance of P. brassicae and C. glomerata. Plant volatiles were significantly induced by herbivory in both healthy and mildew-infected plants, but were quantitatively 41% lower for mildew-infected plants compared to healthy plants. Parasitoids strongly preferred Pieris-infested plants to dually-infested (Pieris + mildew) plants, and preferred dually infested plants over only mildew-infected plants. The performance of P. brassicae was unaffected by powdery mildew, but C. glomerata cocoon mass was reduced when parasitized caterpillars developed on mildew-infected plants. Thus, avoidance of mildew-infested plants may be adaptive for C. glomerata parasitoids, whereas P. brassicae caterpillars may suffer less parasitism on mildew-infected plants in nature. From a pest management standpoint, the concurrent presence of multiple plant antagonists can affect the efficiency of specific natural enemies, which may in turn have a negative impact on the regulation of pest populations.
authors.affiliation: Institute of Biology, University of Neuchâtel, Switzerland.
authors.forename: Gaylord A
authors.identifier: 0000-0003-2701-6582
authors.initials: GA
authors.lastname: Desurmont
authors.affiliation: Institute of Biology, University of Neuchâtel, Switzerland.
authors.forename: Hao
authors.initials: H
authors.lastname: Xu
authors.affiliation: Institute of Biology, University of Neuchâtel, Switzerland.
authors.forename: Ted C J
authors.initials: TC
authors.lastname: Turlings
mesh_terms: D000818:Animals; D001203:Ascomycota / Q000502:physiology*; D029741:Brassica rapa / Q000378:metabolism / Q000382:microbiology*; D002080:Butterflies / Q000469:parasitology*; D005260:Female; D020387:Food Chain; D060434:Herbivory; D006790:Host-Parasite Interactions; D008297:Male; D012903:Smell; D055549:Volatile Organic Compounds / Q000378:metabolism*; D014863:Wasps / Q000502:physiology*
chemical_list: D055549:Volatile Organic Compounds
keywords: Cotesia glomerata; Erysiphe cruciferarum; infochemical networks; insect-plant interactions; multiple herbivory