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

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Since the discovery of Bacillus thuringiensis (Berliner) serovariety israelensis de Barjac (Bti) and efficacious isolates of Bacillus sphaericus Neide, formulations of these bacteria have become the predominant non-chemical means employed for control of mosquito larvae at several locations in the United States and other countries. An overview of developments in the past 20 years is presented in this chapter regarding the toxins of Bti and B. sphaericus, their modes of action, efficacy and factors that affect larvicidal activity, development of resistance, safety, and their roles in integrated mosquito control. The efficacy of Bti formulations has been demonstrated in a variety of habitats against a multitude of species of mosquitoes. B. sphaericus formulations have been utilized predominantly in organically enriched habitats against Culex species, but they are also active in a variety of habitats having low organic enrichment, against numerous species, and across several genera. Stegomyia spp. are not susceptible to practical doses of B. sphaericus formulations. B. sphaericus has been shown to persist longer than Bti in polluted habitats and, under certain circumstances, can recycle in larval cadavers. A disadvantage of B. sphaericus has been the development of resistance in certain populations of Cx. quinquefasciatus Say and Cx. pipiens Linnaeus. Biotic and abiotic factors that influence the larvicidal activity of Bti and B. sphaericus include species of mosquito and their respective feeding strategies, rate of ingestion, age and density of larvae, habitat factors (temperature, solar radiation, depth of water, turbidity, tannin and organic content, presence of vegetation, etc.), formulation factors (type of formulation, toxin content, how effectively the material reaches the target, and settling rate), storage conditions, production factors, means of application and frequency of treatments. Due to their efficacy and relative specificity, both Bti and B. sphaericus can be ideal control agents in integrated programs especially where other biological control agents, environmental management, personal protection and the judicious use of insecticides are combined.

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The influence of simulated sunlight on survival of conidia of 4 species of entomopathogenic Hyphomycetes was investigated. Conidia from 65 isolates ofBeauveria bassiana, 23 ofMetarhizium anisopliae, 14 ofMetarhizium flavoviride and 33 isolates ofPaecilomyces fumosoroseus were irradiated by artificial sunlight (295 to 1,100 nm at an ultraviolet-B irradiance of 0.3 W m(-2)) for 0, 1, 2, 4 and 8 h. Survival was estimated by comparing the number of colony forming units (CFU) produced by conidia exposed to irradiation to the number of CFUs produced by an unexposed control. Survival decreased with increased exposure to simulated sunlight; exposure for 2 h or more was detrimental to all isolates tested. Overall, isolates ofM. flavoviride were the most resistant to irradiation followed byB. bassiana andM. anisopliae. Conidia ofP. fumosoroseus were most susceptible. In addition to the large interspecies differences in susceptibility to irradiation, there was also an intraspecies variation indicating that strain selection to irradiation tolerance may be important in the development of microbial control agents where increased persistence in an insolated environment is desirable.