Entomopathogenic nematodes (EPNs) have recently demonstrated effectiveness against the navel orangeworm, Amyelois transitella (Walker), a key pest of pistachios in California. Determining the spatial distribution, temporal persistence, and ecological impacts of EPNs can help explain, and perhaps enhance, their efficacy in this system. Our objectives in this study were to determine the population structure of EPNs and their impact on soil communities. S. carpocapsae was applied through the irrigation system of a 16.2-acre pistachio orchard in Madera county, CA at a rate of 5 X 10 ⁸ infective juviniles/acre. We collected soil samples near 45 trees before and two weeks after S. carpocapsae were applied. We assessed the presence of EPNs using Galleria baiting and in situ collection tubes. Other nematodes and soil arthropods were extracted using Baermann and Berlese funnels, respectively. We identified nematodes and soil arthropods to the genus or family level and correlated the presence of EPNs with soil faunal diversity.