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ARS Home » Plains Area » Brookings, South Dakota » Integrated Cropping Systems Research » Research » Publications at this Location » Publication #318250

Title: Mutualistic and antagonistic trophic interactions in canola: the role of aphids in shaping pest and predator populations

item LAYMAN, MARISSA - South Dakota State University
item Lundgren, Jonathan

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2015
Publication Date: 7/26/2015
Citation: Layman, M., Lundgren, J.G. 2015. Mutualistic and antagonistic trophic interactions in canola: the role of aphids in shaping pest and predator populations. Biological Control. 91:62-70.

Interpretive Summary: Food webs are complex, and the interactions of species within these food webs can have important implications for when and where pests become problems. This study focuses on canola, and the complex interactions between herbivores and predators within South Dakota canola fields. Ants tend aphids as a form of livestock, and protect these herbivores against predators. Nevertheless, aphids represent an important nutritional resource for many predator species in spite of the ants. Our research found strong correlations among these groups of insects; essentially aphids in canola supported a suite of natural enemies and mutualists. As aphid populations declined, so too did this predator community. The resulting dearth of predators (and competitive herbivores) gave rise to a more notorious pest, the imported cabbageworm. Thus, the complex interactions between aphids and natural enemies may be an important source of biotic resistance to the proliferation of other pests in the canola system.

Technical Abstract: Aphids have important effects on the abundance and occurrence of tending ants, predators, and pests in agronomic systems, and DNA-based gut content analysis can aid in establishing predator-prey interactions. The purpose of this study was to determine how the presence of aphids, ants, and pest individuals interact within canola fields. Using seasonal data from canola fields, the relationships among ants, aphids and pest individuals were determined, along with the use of PCR techniques in order to amplify aphid DNA and confirm food web links on predators who consume aphids. We determined that aphid presence positively influences the number of ants and predators in a community, and diminishing aphid populations over the growing season were associated with declines in both ants and predators. These reduced populations of predators and aphids may have provided the opportunity for a key pest, Pieris rapae to build populations as the season ensued. This research suggests that complex interactions among herbivores and shared predators contribute to pest outbreaks.