Tritrophic effects of host plants on an herbivore-pathogen interaction

Aaron J. Gassmann, S. Patricia Stock, Bruce E. Tabashnik, Michael S. Singer

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Tritrophic interactions may include directly harmful effects of host plants on herbivores, and directly or indirectly harmful effects of host plants on the natural enemies of herbivores. Tritrophic interactions involving parasitoids and predators have received considerable attention but less is known about how host plants affect entomopathogens. We compared growth and resistance to entomopathogenic nematodes for "woolly bear" caterpillars, Grammia incorrupta (=geneura) (Hy. Edwards) (Lepidoptera: Arctiidae) fed lettuce, Lactuca sativa L. (Asteraceae), versus threadleaf groundsel, Senecio longilobus Benth. (Asteraceae). Both plants are members of the Asteraceae, but only S. longilobus contains pyrrolizidine alkaloids. Caterpillars gained more mass when fed L. sativa compared with S. longilobus; yet, in one of four cases studied, resistance to nematodes was higher when caterpillars ate S. longilobus. Caterpillar resistance to nematodes did not differ between host plants in the other cases. In addition, nematode reproduction was higher in cadavers of G. incorrupta that had been fed L. sativa instead of S. longilobus, suggesting that S. longilobus had indirectly detrimental effects on entomopathogenic nematodes. Our results illustrate how trade-offs may arise in tritrophic interactions involving entomopathogens, as the cost of decreased growth imposed by S. longilobus was accompanied by the benefit of greater resistance to entomopathogenic nematodes.

Original languageEnglish (US)
Pages (from-to)371-378
Number of pages8
JournalAnnals of the Entomological Society of America
Issue number3
StatePublished - May 2010


  • Alkaloids
  • Entomopathogenic nematodes
  • Pathogen reproduction
  • Polyphagy
  • Tradeoff

ASJC Scopus subject areas

  • Insect Science


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