A review of open-field host range testing to evaluate non-target use by herbivorous biological control candidates

Authors: SCHAFFNER, URS - Commonwealth Agricultural Bureau International (CABI) - Switzerland; Smith, Lincoln; CRISTOFARO, MASSIMO - Enea Casaccia Research Center

Submitted to: BioControl
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2018
Publication Date: 6/1/2018
Citation: Schaffner, U., Smith, L., Cristofaro, M. 2018. A review of open-field host range testing to evaluate non-target use by herbivorous biological control candidates. Biocontrol. 3(405-416). doi.org/10.1007/s10526-018-9875-7.
DOI: https://doi.org/10.1007/s10526-018-9875-7

Interpretive Summary: Classical biological control is a cost-effective, sustainable, and environmentally friendly method to control invasive alien weeds. The method involves searching for insects that attack target weeds in their region of origin, testing them to be sure that they do not attack other nontarget plants, and releasing them to control the target weed. Safety depends on correctly assessing the potential risk of agents to nontarget plants. However, some nontarget plants may be attacked in laboratory experiments that are not normally attacked in the field. Open field experiments provide a strategy to assess host specificity under conditions that are more natural. This paper reviews 76 studies that were conducted during the past 50 years. The results indicate an increasing use of this strategy, especially to help clarify the results of laboratory or cage experiments and refine our understanding of the risk posed to nontarget plant species. We expect the method to continue to be used, especially to address specific hypotheses about the host specificity of prospective biological control agents of weeds.

Technical Abstract: One of the fundamental challenges of pre-release studies in classical biological weed control is to assess and predict the likelihood and consequences of non-target effects. Unless a candidate biological control agent is strictly monophagous, open-field host range studies are an important tool to predict the likelihood of non-target effects since they provide the opportunity to study host selection of herbivores when displaying the whole array of pre- and post-alighting behavior. Over the course of its 50 years history, the purpose and the design of open-field host range studies have changed considerably, with more recent studies aiming to clarify or refine specific questions related to one or a few test plant species and using a set design. We discuss the opportunities and challenges of this approach and suggest that future open-field host range studies should be more hypothesis-driven and apply different experimental designs that facilitate the interpretation of their results.