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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGICAL CONTROL OF SWALLOW-WORTS, INVASIVE WEEDS OF THE NORTHEASTERN UNITED STATES

Location: Biological Integrated Pest Management Unit

Title: Plant-mediated interactions: considerations for agent selection in weed biological control programs

Authors
item Milbrath, Lindsey
item Nechols, James -

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 17, 2014
Publication Date: February 26, 2014
Citation: Milbrath, L.R., Nechols, J.R. 2014. Plant-mediated interactions: considerations for agent selection in weed biological control programs. Biological Control. 72:80-90.

Interpretive Summary: Plant-feeding insects or plant diseases can interfere with or help one another indirectly by feeding on and causing changes in the quality or abundance of host plants they share. These plant changes, caused by one insect or disease, may result in positive or negative effects on the other plant-feeding species even if they feed on different plant parts or attack the plant at different times of the year. In the case of weeds, indirect interactions between insects or pathogens used for biological control may have important consequences for weed suppression. However, little attention has been given to this issue. We provide a brief review of these plant-mediated interactions and their importance to weed biological control, and then make recommendations for how experiments should be conducted to evaluate when and where plant-mediated interactions occur between biological control agents and how they impact weeds. We also provide tables that show various outcomes of plant-mediated effects on biological control agents and target weeds to help practitioners in making decisions about which biological control agents to release for greatest impact. We use a case study based on our research of musk thistle weevils to illustrate the usefulness of evaluating plant-mediated interactions, and the kind of decisions that would be made. Investigating plant-mediated interactions should result in better predictions about which biological control agent (or agent combinations) should be released for weed biological control programs.

Technical Abstract: Plant-mediated indirect interactions among herbivores (arthropods and pathogens) are common and extensively reported in the ecological literature. However, they are not well-documented with respect to weed biological control. Such interactions between biological control agents can have net positive or negative impacts on total weed suppression depending on the strength of the interaction(s), the relative importance of the agent indirectly impacted, and the combined weed suppression that results. A better understanding of plant-mediated interactions may improve decision-making about which agents to introduce in classical biological control programs for greatest impact on invasive weeds. This paper reviews the subject, including examples from the biological control literature; outlines the need for research on indirect effects of herbivores on other herbivores; discusses how such knowledge may strengthen classical biological control programs for invasive weeds; and provides recommendations for the kind of studies that should be done and how information about plant-mediated interactions could be integrated into agent evaluation protocols, to assist in decision-making about agents for importation and release.

Last Modified: 12/18/2014
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