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Effects of fertilizer, fungal endophytes and plant cultivar on the performance of insect herbivores and their natural enemies

  1. JOCHEN KRAUSS1,
  2. SIMONE A. HÄRRI1,
  3. LOWELL BUSH2,
  4. RENÉ HUSI1,
  5. LAURENT BIGLER3,
  6. SALLY A. POWER4,
  7. CHRISTINE B. MÜLLER1

Article first published online: 27 NOV 2006

DOI: 10.1111/j.1365-2435.2006.01216.x

Issue

Functional Ecology

Functional Ecology

Volume 21, Issue 1, pages 107–116, February 2007

Additional Information

How to Cite

KRAUSS, J., HÄRRI, S. A., BUSH, L., HUSI, R., BIGLER, L., POWER, S. A. and MÜLLER, C. B. (2007), Effects of fertilizer, fungal endophytes and plant cultivar on the performance of insect herbivores and their natural enemies. Functional Ecology, 21: 107–116. doi: 10.1111/j.1365-2435.2006.01216.x

Author Information

  1. 1

    Institute of Environmental Sciences, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland,

  2. 2

    Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY 40546-0091, USA,

  3. 3

    Institute of Organic Chemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland,

  4. 4

    Division of Biology, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK

*†Author to whom correspondence should be addressed. E-mail: jkrauss@uwinst.unizh.ch

Publication History

  1. Issue published online: 27 NOV 2006
  2. Article first published online: 27 NOV 2006
  3. Received 20 June 2006; revised 25 August 2006; accepted 15 September 2006Editor: J. Daniel Hare

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Keywords:

  • cereal aphids;
  • endophytic fungi;
  • Neotyphodium lolii;
  • parasitoids;
  • trophic cascades

Summary

  • 1
    Endophytic fungi are associates of most species of plants and may modify insect community structures through the production of toxic alkaloids. Fertilization is known to increase food plant quality for herbivores, but it is also conceivable that additional nitrogen could increase the production of the insect toxic alkaloid, peramine, in endophyte-infected plants.
  • 2
    The relative importance of soil fertility and endophyte infection on herbivores and their natural enemies is unknown. As performance of the host plant is often affected by an interaction between endophyte infection and genetic background, four different plant cultivars were tested. The main questions addressed in this study were whether plant cultivar and fertilizer addition to endophyte-infected and endophyte-free Lolium perenne affect alkaloid concentrations, plant life-history traits and the abundances of aphid species and their parasitoids.
  • 3
    In a full factorial outdoor experiment we found a strong positive effect of fertilizer on plant biomass and on the abundance of aphids and parasitoids. While plant traits differed between cultivars, there was little effect of cultivar on either aphid or parasitoid abundance. Only endophyte-infected plants contained alkaloids, and the concentration of peramine was enhanced in fertilized plants. However, endophyte infection had no negative effect on aphid or parasitoid abundances. Plant traits were only weakly influenced by endophyte infection in the field, which contrasts with plant growth room studies, where both germination rate and plant height were influenced by endophyte–cultivar interactions.
  • 4
    The generally weak effects of endophytes in the outdoor experiment could be explained by various additional constraints under field conditions and the relatively low peramine concentration that we observed.
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