Please cite this article as: Lacey, L.A., Grzywacz, D., Shapiro-Ilan, D.I., Frutos, R., Brownbridge, M., Goettel, M.S., Insect pathogens as biological control agents: back to the future, Journal of Invertebrate Pathology (2015), doi: http://dx.doi.org/10.1016/j. jip.2015.07.009 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. The development and use of entomopathogens as classical, conservation and augmentative 26 biological control agents have included a number of successes and some setbacks in the past 15 27 years. In this forum paper we present current information on development, use and future 28 directions of insect-specific viruses, bacteria, fungi and nematodes as components of integrated 29 pest management strategies for control of arthropod pests of crops, forests, urban habitats, and 30 insects of medical and veterinary importance. 31Insect pathogenic viruses are a fruitful source of MCAs, particularly for the control of 32 lepidopteran pests. Most research is focused on the baculoviruses, important pathogens of some 33 globally important pests for which control has become difficult due to either pesticide resistance 34 or pressure to reduce pesticide residues. Baculoviruses are accepted as safe, readily mass 35 produced, highly pathogenic and easily formulated and applied control agents. New baculovirus 36 products are appearing in many countries and gaining an increased market share. However, the 37 absence of a practical in vitro mass production system, generally higher production costs, limited 38 post application persistence, slow rate of kill and high host specificity currently contribute to 39 of Bt toxins, has been conducted over the past two decades. The Bt genes used in insect-resistant 54 transgenic crops belong to the Cry and vegetative insecticidal protein families of toxins. Bt has 55 been highly efficacious in pest management of corn and cotton, drastically reducing the amount 56 of broad spectrum chemical insecticides used while being safe for consumers and non-target 57 organisms. Despite successes, the adoption of Bt crops has not been without controversy. 58

An overview of is presented of the major factors (pathogen, insect host and environment) influencing the efficacy of hypomycetous fungi for biological control. Examples are given of the successful use of entomopathogenic Hypomycetes (including Aschersonia spp., Beauveria bassiana, B. brongniartii, Metarhizium anisopliae, Paecilomyces fumosoroseus and Verticillium lecanii) in pest control, emphasizing some of the strategies that can be used to optimize their impact on pest populations.

An important mechanism for insect pest control should be the use of fungal entomopathogens. Even though these organisms have been studied for more than 100 years, their effective use in the field remains elusive. Recently, however, it has been discovered that many of these entomopathogenic fungi play additional roles in nature.They are endophytes, antagonists of plant pathogens, associates with the rhizosphere, and possibly even plant growth promoting agents. These findings indicate that the ecological role of these fungi in the environment is not fully understood and limits our ability to employ them successfully for pest management. In this paper, we review the recently discovered roles played by many entomopathogenic fungi and propose new research strategies focused on alternate uses for these fungi. It seems likely that these agents can be used in multiple roles in protecting plants from pests and diseases and at the same time promoting plant growth.

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