Does floral nectar improve biological control by parasitoids?

George E. Heimpel, Mark A. Jervis

Research output: Chapter in Book/Report/Conference proceedingChapter

188 Scopus citations


Introduction The incorporation of plant diversity within agricultural systems has led to decreased insect pest densities in approximately 50% of studies in which monocultures and polycultures were directly compared (Risch et al. 1983; Andow 1991; Coll 1998; Gurr <italic>et al. 2000). One of the leading hypotheses explaining the observation of decreased pest densities under polycultures is that increased plant diversity can enhance the action of natural enemies of pests (the “enemies hypothesis” of Root 1973). Increased plant diversity can provide natural enemies with resources such as a favorable microclimate, alternative hosts or prey, or plant-based foods such as pollen, nectar, or honeydew (Landis et al. 2000). In this chapter, we focus on one of the more intuitively clear predictions encompassed within Root's enemies hypothesis – the idea that the presence of nectar-producing plants can improve biological control of pests by supplying parasitoids with sugar. Note that this idea includes two components: an outcome (improved biological control) and an underlying mechanism (nectar-feeding), both of which need to be demonstrated. We refer to the combined outcome and mechanism as the “parasitoid nectar provision hypothesis”. The hypothesis that plant diversification can decrease pest pressure by providing sugar to parasitoids that would otherwise be sugar-limited has its origins in anecdotal or semi-quantitative observations of increased parasitism rates and biological control in the vicinity of flowering plants.

Original languageEnglish (US)
Title of host publicationPlant-Provided Food for Carnivorous Insects
Subtitle of host publicationA Protective Mutualism and its Applications
PublisherCambridge University Press
Number of pages38
ISBN (Electronic)9780511542220
ISBN (Print)0521819415, 9780521819411
StatePublished - Jan 1 2005


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