Use of Ecological Theory to Understand the Efficacy and Mechanisms of Multistrain Biological Control.

Since the 1970s, over 6,500 articles have been published about microbial biocontrols and over 200 microbial isolates have been registered for commercial use. However, many of these solutions have seen limited use due to limitations with their in-field efficacy. Even when multiple biocontrol agents are combined to create multistrain biocontrols, the resulting combinations can be less effective than the individual agents. One likely contributor is due to how multistrain microbial biocontrols are created. Multistrain microbial biocontrols are generally produced under controlled settings that are divorced from the ecological conditions they will need to function under. Traditionally, researchers culture, identify, and screen isolates for pathogen suppression traits. Then these researchers will combine the most promising isolates in an attempt to create more effective solutions. This approach, while effective for identifying suppressive isolates and determining the mechanisms of pathogen suppression, does not take into consideration the variability of natural environments, nor the complex ecological interactions that occur between plant hosts, pathogens, and component biocontrol agents, thus limiting the range of circumstances that these multistrain solutions can reliably succeed. To address these limitations, we suggest the application of relevant ecological theory to determine which isolates should be combined to create more reliable multistrain biocontrols. In this synthesis, we build on prior work focused on addressing plant pathogens through the use of multistrain microbial biocontrols, but we argue that viewing this work through the lens of ecology reveals key "design principles" from natural communities that are stable, functioning, and comprise multiple species.