Fungi have been known to attack insects and mites for thousands of years. Although the causative agent of fungal disease of insects was not always understood, insects infected with fungi were recorded by the Chinese in the seventh century (Tanada and Kaya 1993) and drawings of Cordyceps infections abound in early 18th and 19th century literature. The first experimental demonstration of a microbe as a disease-causing organism was by Agostino Bassi, published in 1835-1836, in Italy, with the silkworm pathogenic fungus, Beauveria bassiana. He demonstrated that the fungus causes insect death and could be transmitted to other silkworms. It was not long after the first demonstration of the devastating impact of an entomopathogenic fungus on a beneficial insect that it occurred to researchers that disease may be a useful method for control of insect pests. Pasteur is credited with the early proposition that fungi could be used to control a pest insect. He proposed that a fungus could be used against Phylloxera in grapevines, a pest eventually controlled using copper solutions. However, it was the Nobel Prize winning researcher, Elie Metchnikoff, who first developed a fungus as a practical control agent for application to a pest. Working in Russia from 1878, Metchnikoff developed the fungus Metarhizium anisopliae for control of the cereal cockchafer, Anisoplia austriaca, then a devastating pest. Metchnikoff carried out the first successful infection experiments with larvae of A. austriaca and the sugar beet weevil, Cleonus punctiventris, and initiated mass production of the fungus for field experiments (Zimmermann et al. 1995). With the mass production of M. anisopliae, Metchnikoff applied a biotechnological approach to entomopathogenic fungi for the first time, a precursor to the development of biopesticides. The first actual field application of M. anisopliae in Russia was left to Krassilstchik (1888) who mass produced the fungus and applied it in the field for sugar-beet weevil control.
Despite the early discovery of their potential, it was only recently that entomopathogenic fungi have been utilized successfully in biocontrol programs. The fungi are often effective as natural control agents, but their activity is very dependent upon environmental conditions. Many have restrictive temperature ranges for germination, infection, and sporulation, or high humidity requirements for sporulation and spore germination. In some cases, the infective stage is not robust and, as many of the most promising candidate fungi for pest control have lost the ability to form persistent stages such as resting spores, storage and application can be problematic. Variation within species or clusters of species has not been well understood, thus strain selection has not often been attempted or not been possible. The application of biotechnology to the study and development of entomopatho-genic fungi has the potential to overcome some of these limitations. Biotechnology has contributed to all areas in the development of entomopathogenic fungi as biocontrol agents, from identification to formulation. This chapter reviews the contribution of biotechnology to the development of entomopathogenic fungi.
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