The Current State and Future Potential of Microbial Control of Scarab Pests

Injury and control costs for the invasive scarab Japanese beetle (Family Scarabeidae, Popillla japonica) alone is estimated at $450 million per year in the U.S. Chemical controls are commonly used to control scarab pests, but concerns about human safety and negative impacts on beneficial and non-target organisms, such as pollinators, are increasingly driving the market towards less toxic and more environmentally friendly management options. Microbial entomopathogens are excellent candidates for biopesticides and biocontrol agents. Although microbial pesticides currently make up only 1–2% of the insecticide market, the discovery and development of new microbes are increasing. Microbial products are non-toxic to humans and most are species-specific, reducing non-target effects. While some are slow-acting, others provide rapid control and some can be as efficacious as chemical insecticides, particularly when used in combination. Another major advantage of microbial controls is that many can persist in the environment, and become biocontrol agents, providing long-term control and reducing costs. This article provides a summary of the microbial entomopathogens that are known to infect scarab beetle species including bacterial, fungal, viral, microsporidian, and protozoan taxa, as well as the existing formulations and their efficacy. Lesser-known microbial species are also discussed as potential future controls. We also discuss the development of new techniques for improving efficacy, such as genetic engineering, synergistic interactions, auto-dissemination strategies, and improved formulations.