NATURAL DISTRIBUTION OF ENTOMOPATHOGENIC NEMATODES (RHABDITIDA, HETERORHABDITIDAE AND STEINERNEMATIDAE) IN OREGON SOILS

To determine the natural distribution of entomopathogenic nematodes (H eterorhabditidae and Steinernematidae) in Oregon, 255 soil samples wer e taken from 59 sites representing ecologically diverse habitats and d ifferent geographic regions of the state. The presence or absence of e ntomopathogenic nematodes in samples was determined using the Galleria mellonella (L.) bioassay. Entomopathogenic nematides were recovered f rom 30 soil samples representing 14 different sites. Twenty-four soil samples from 10 sites contained Heterorhabditis spp. and seven samples from five sites contained Steinernema spp. We found significant assoc iation among geographic regions, habitats, soil textures, and genera o f nematodes recovered. More Heterorhabditis spp. were recovered than S teinernema spp. at the high latitude of Oregon. Geographic region and soil texture may be the most important factors influencing the natural distribution of Heterorhabditis spp. in Oregon.