Biological control agents for white grubs (Coleoptera : Scarabaeidae) in anticipation of the establishment of the Japanese beetle in California

We tested biological control agents for the control of 3rd-instar scarab tu rfgrass pests, both for the masked chafer Cyclocephala hirta LeConte and th e Japanese beetle, Popillia japonica Newman. The former species is endemic in California whereas the latter, although not yet established, constitutes a permanent serious threat to agriculture and horticulture in California. We conducted experiments using C, hirta in California and P, japonica in Ne w Jersey. A field trial conducted in 2 different California turfgrass sites compared the field persistence in the absence of hosts of Bacillus thuring iensis Berliner subspecies japonensis Buibui strain, the milky disease bact erium, Paenibacillus (=Bacillus) popilliae (Dutky), and the entomopathogeni c nematodes Steinernema kushidai Mamiya and Heterorhabditis bacteriophora P oinar to that of the organophosphate diazinon. Soil samples taken 0-70 d af ter applications were bio-assayed with P, japonica. Only diazinon and the e ntomopathogenic nematode S. kushidai caused substantial mortality and S. ku shidai activity persisted significantly longer than diazinon activity. In g reenhouse experiments, combinations of entomopathogenic nematode species us ually resulted in additive mortality of scarab larvae. Combinations of S, k ushidai and diazinon also resulted in additive mortality. In field trials, the efficacy of H. bacteriophora and especially S. kushidai and S. glaseri, was comparable to that of diazinon over 14-18 d. However, it is likely tha t at least S. kushidai would have outperformed diazinon over an extended pe riod because of its longer persistence and potential for recycling in the h osts. S. kushidai, should it become commercially available, deserves furthe r examination as an alternative to chemical white grub control especially a s a highly compatible component of sustainable turfgrass management.