"Three experiments were designed to evaluating the effects of Ovavesicula popilliae, a species-specific microsporidian pathogen, on Japanese beetle (Popillia japonica) in Michigan. In the first experiment prevalence of O. popilliae, in Michigan was determined by collecting host larvae and adults at 47 golf courses or rest areas in 2018 and 2019. Larvae and adults were dissected and assessed for O. popilliae infection. Infection and scarab species data from nine of the golf courses visited in 2018 was compared to similar data from the same nine golf courses from 1999. The survey of golf courses and highway rest areas in Michigan documented a significant decline of Japanese beetle in the 20 year-period since the last survey, and the slow spread of Ovavesicula popilliae. At introduction sites from the last 12 years O. popilliae established and persisted at epizootic levels.In the second experiment survival of Ovavesiucla popilliae-infected larvae was compared with survival of healthy larvae during their overwintering period, from October to May, in two consecutive years of experiments. Ovavesicula popilliae infection of larvae at the beginning of the experiment (34.0 and 26.9%, in October 2017 and October 2018, respectively) and soil cores from a site where the pathogen was active had a significant impact on the survival of infected larvae (90-100% reduction). In the third experiment healthy Japanese beetle larvae were inoculated by placing them in soil cores collected from a site where O. popilliae had established and became epizootic. Infection and survival of inoculated larvae was compared with the same for healthy Japanese beetle larvae from October to May. There was no difference in percent infection of inoculated larvae (5.0 %) and control larvae (1.8%). This may be because the field plots for this study were placed directly over the top of field plots from the previous year where infected larvae were put into turf and soil cores."--Page ii.
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