BIOLOGICAL CONTROL-MICROBIALS Association of Ovavesicula popilliae (Microsporida: Ovavesiculidae) With Winter Mortality of Larvae and Reduced Fecundity of Female Japanese Beetles (Coleoptera: Scarabaeidae)

Populations of Japanese beetle at sites in Michigan where Ovavesicula popilliae (Andreadis) was introduced in 1999 and 2000 were compared with nearby control sites from fall of 2005 through spring of 2008. Percent infection byO. popilliae andwinter mortality of Japanese beetle were determined by sampling larvae in October and April from 12 golf holes on six courses in southeast Michigan and eight holes on four courses in southwest Michigan. Adult Japanese beetles were also collected from these golf courses in July and August of 2007 to determine the impact of O. popilliaeinfection on egg development in females. In southeast Michigan, O. popilliae appeared to spread rapidly from the 100 m plots where it was previously introduced to surrounding golf course holes between 2000 and 2006.However, data from southwestMichigan suggests thatO. popilliaehad already been introduced into the area. Regression analysis of data from all 20 golf course holes gives a signiÞcant relationship between percent infection of larvae with O. popilliae and winter mortality of Japanese beetle. Meanwinter mortality of larvae around golf course holes where 10%were infected with O. popilliae was 24.7% compared with 41.7% mortality where 10Ð30% were infected, and 72.0% mortality where 30%were infected. Females infectedwithO. popilliae contained 50% fewermature eggs than uninfected females. In addition, females from golf courses where all of the fairways and roughs were treated annually with imidacloprid contained 48% fewer mature eggs than females from golf courses where insecticides were only used on the fairways or not at all.