Association ofOvavesicula popilliae(Microsporida: Ovavesiculidae) With Winter Mortality of Larvae and Reduced Fecundity of Female Japanese Beetles (Coleoptera: Scarabaeidae)

Abstract

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 by O. popilliae and winter 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. popilliae-infection on egg development in females. In southeast Michigan, O. popilliae appeared to spread rapidly from the 100 m(2) plots where it was previously introduced to surrounding golf course holes between 2000 and 2006. However, data from southwest Michigan suggests that O. popilliae had already been introduced into the area. Regression analysis of data from all 20 golf course holes gives a significant relationship between percent infection of larvae with O. popilliae and winter mortality of Japanese beetle. Mean winter mortality of larvae around golf course holes where <10% were infected with O. popilliae was 24.7% compared with 41.7% mortality where 10-30% were infected, and 72.0% mortality where >30% were infected. Females infected with O. popilliae contained 50% fewer mature 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.

Comparison of Scarab Grub Populations and Associated Pathogens and Parasitoids in Warm- or Cool-Season Grasses Used on Transitional Zone Golf Courses

“…A strain of Serratia infective to the scarab C. zealandica has been developed as a commercial biocontrol in New Zealand (Jurat-Fuentes and Jackson 2012). Although neither Stictospora nor Ovavesicula have been commercially developed, introduction of Ovavesiculainfected P. japonica grubs to sites in Michigan showed promise for establishing the pathogen where it previously was absent (Smitley et al 2011). The current study suggests that grass species is unlikely to strongly affect performance of current or future microbial insecticides against root-feeding scarab grubs.…”

“…It is possible that sublethal infection by other "weak" pathogens (e.g., Ovavesicula and Stictospora), or our holding grubs in cups with soil and grass seedlings for disease expression, could have weakened and predisposed some grubs to infection by Serratia or Paenibacillus. For example, there is some evidence that milky disease incidence tends to be higher at Þeld sites where O. popilliae is established (Hanula 1990, Smitley et al 2011.…”

“…Pathogen infection may, for example, reduce grubsÕ overwintering capability Potter 2010, Smitley et al 2011) or fecundity of surviving adults (Hanula 1990, Smitley et al 2011 or increase host susceptibility to other pathogens (Hanula 1990, Smitley et al 2011. Although incidence of individual natural enemies may be relatively low, their collective impact over the 10 Ð11-mo period that grubs develop in the soil may be substantial.…”

Survey of pathogens and parasitoids of Popillia japonica (Coleoptera: Scarabaeidae) in northwest Arkansas

“…It has been found naturally occurring in low prevalence in other areas (Cappaert and Smitley, 2002;Redmond and Potter, 2010) and has also been artificially introduced to try to reduce P. japonica populations in Michigan (Cappaert and Smitley, 2002;Smitley et al, 2011). O. popilliae appears to spread slowly with the expanding Japanese beetle population as indicated by Michigan (Cappaert and Smitley, 2002) and Kentucky surveys (Redmond and Potter, 2010).…”