EFFICACY OF ENTOMOPATHOGENIC NEMATODE STRAINS AGAINST POPILLIA-JAPONICA (COLEOPTERA, SCARABAEIDAE) LARVAE

Control of Japanese beetle (Popillia japonica Newman) larvae by Heterorhabditis bacteriophora Poinar (HP88 strain and a New Jersey strain, NJ-2) and Steinernema glaseri Steiner (NC strain and a New Jersey strain, NJ-43) showed that all strains reduced larval populations to a level comparable with that achieved by use of bendiocarb. Nematode strains and species did not differ significantly in mean level of population reductions (H. bacteriophora HP88 and NJ-2, 51.0 and 71.6%; S. glaseri NC and NJ-43, 50.4 and 70.1%, respectively). However, variation in the level of population reduction provided by NJ-43 was less than that by the NC strain. After a 3-wk test period, nematode persistence and downward migration in the field did not differ among species and strains. In a laboratory bioassay, New Jersey strains provided higher levels of larval mortality compared with strains cultured in the laboratory for at least a decade. A new method used to count viable bacteria retained by individual infective juveniles showed that NJ-43 not only retained more bacteria than the NC strain (19.5 +/- 0.2 compared with 4.9 +/- 0.06 bacteria per infective juvenile) but also that the proportion of nematodes retaining bacteria was higher (77% compared with 55%). Bacterial retention by infective juveniles did not differ significantly between H. bacteriophora strains.