IMPACT OF BACILLUS-POPILLIAE, RICKETTSIELLA POPILLIAE AND ENTOMOPATHOGENIC NEMATODES ON A POPULATION OF THE SCARABAEID, CYCLOCEPHALA HIRTA

Larvae of the scarabaeid, Cyclocephala hirta, are major pests of turfg rass in California, A field test was conducted against third instars t hat included the following treatments. untreated control; chemical ins ecticide (bendiocarb); milky disease bacterium (Bacillus popilliae); a nd entomopathogenic nematodes (Steinernema feltiae and Heterorhabditis bacteriophora). There were no significant differences in population r eduction among the treatments, but the larval population in all plots showed a dramatic decline. The C. hirta population had a natural occur rence of milky disease and blue disease caused by Rickettsiella popill iae. The prevalence of blue disease during the course of the study ave raged < 10% but that of milky disease averaged about 20%. More signifi cantly the soil fi om all treatment plots when bioassayed for B. popil liae showed that 67-90% of the larvae became infected with this bacter ium. None of the larvae became infected with the blue disease organism . We conclude that B. popilliae was occurring in epizootic proportions in our field tests and was a significant mortality factor in causing the decline of the C. hirta population.