Parasitoids and pathogens of Japanese beetle (Coleoptera: Scarabaeidae) in southern Michigan

Abstract

The density of Japanese beetle (Popillia japonica Newman) and the prevalence of its natural enemies were evaluated in southern Michigan. Third instars were collected in spring and fall and adults during the summer of 1999 and 2000 at 11 golf courses. Larvae were also collected once in fall of 2000 from 24 additional sites including golf courses (n = 8), blueberry farms (n = 7) and low-maintenance turf (n = 9). Larval density in the irrigated rough at the 11 primary golf course sites averaged 9.5/0.1 m2 (range, 3.7-21.0). At the 24 additional sites, where habitat was more diverse, Japanese beetle larval density averaged 2.9/0.1 m2 (range, 0.60-14.4). The larval parasitoid Tiphia vernalis Rohwer and the adult parasitoid Istocheta aldrichi (Mesnil) were absent from all sites in this study. Cephaline gregarines (Stictospora sp.) were the most common parasites, infecting 36.1% of all larvae in fall of 2000. The microsporidean Ovavesicula popilliae Andreadis was absent at all but two locations near Kalamazoo, MI. The bacterial pathogen Paenibacillus popilliae (Dutky) and entomopathogenic nematodes were uncommon, infecting <1% of larvae. Overall, two parasites (T. vernalis and I. aldrichi) and two pathogen (O. popilliae), reported to be widespread and epizootic in some eastern states, were absent or nearly so (O. popilliae was found at two of 35 locations) in Michigan. Stictospora sp. was found at most locations in Michigan (25/36) where Japanese beetle infestations have been active for more than 20 yr, but was scarce or absent from areas where Japanese beetle has become established in the last 10 yr.