Entomopathogenic fungi infect some arthropod pest and have been used for biological control. Some entomopathogenic fungi have high potential in insect pest management worldwide, and most of researches were given to Hypocreales order of Ascomycota, but little in Zygomycota, such as Entomophthorales in our country. We have identified some species belonging to Entomophthorales and investigated cultural features and ecology of Entomophaga aulicae. E. aulicae in sweet potato fields, where Aedia leucomelas was a dominant pest, had caused epizootics from 2002–2005. E. aulicae-infected A. leucomelas larva were mostly found from August to October and its occurrence was significantly related to the precipitation. E. aulicae were mainly observed in dead A. leucomelas larval populations (infection rate = 41.3% in 2002), rather than other lepidopteran pests. E. aulicae was morphologically and genetically identified and its virulence was characterized in laboratory conditions. Additionally, pest infection by Zoophthora radicans, Neozygites floridana and some Entomophthorales have been identified. On the basis with this information, we need research to predict the prevalence and to develop biological control agent using Entomophthorales including E. aulicae that contribute to regulation of host populations.