ConclusionThe study of enemy-risk effects has advanced greatly in the past two decades, developing into a more fully realized field, incorporating theoretical frameworks, many experimental methods, and even predictive models. However, the field of biological control is still catching up to broader natural enemy ecology, and the incorporation of enemy-risk effects into the biocontrol framework is still in its infancy. There is a significant body of research documenting the importance of risk effects in biocontrol systems, but there is much room to grow beyond this. We have outlined several areas in which risk effect literature may provide insight into biocontrol practice, and hope that further studies will investigate specific interactions between enemy-risk effects and IPM programs more thoroughly.
Community ecologists likewise can find, in biological control systems, rich examples where the consequences of risk effects play out in well-characterized predator-prey systems, including both coevolved versus novel predator-prey associations. Agricultural systems provide ideal settings for examining both the shorter- and the longer-term consequences of risk effects, on both smaller and larger spatial scales. Opportunities exist to examine how risk effects shape trophic cascades, the distributions of prey populations in space, and even microevolutionary responses to plant defensive traits.
One of the most crucial aspects of the merging of the fields will be broadly considering biocontrol of arthropods as an inherently behavioral issue. A focus on preventing unwanted and damaging pest behavior, whether through killing pests or changing their behavior, broadens the scope of interactions that may be utilized in biological control. The historical focus on population density is no longer sufficient in light of research demonstrating the importance of enemy-risk effects and how they can cascade to the level of plants.
Studies of risk effects in biocontrol systems should also include more holistic studies of the numerous interactions, either synergistic or antagonistic, between pest behavior and broader IPM practices. Studies in this area can simultaneously investigate core ecological concepts and provide more concrete suggestions for biocontrol practitioners.
Finally, we recognize that it may not be feasible to investigate all possible enemy-risk effects in a given agroecosystem when attempting to predict the effects of a biocontrol agent, which is why we propose the incorporation of theory and predictive models from risk effect research into biocontrol decision-making processes. By considering the evolutionary history of the pest, bottom-up effects of the crop, and spatiotemporal dynamics of the agroecosystem, pest management programs may be able to predict the relative importance of various types of risk effects and how they may interact with management practices. Just as other detailed aspects of pest and agent biology are incorporated into management decisions, we advocate for the inclusion of enemy-risk effect knowledge as well.