Technical Abstract: The objective of this study was to determine the susceptibility of the strawberry crown moth, Synanthedon bibionipennis (Lepidoptera: Sesiidae) larvae to two species of entomopathogenic nematodes(Steinernema carpocapsae (Weiser) Agriotos and Heterorhabditis bacteriophora (Steiner) Oswego). Nematodes were evaluated in laboratory soil bioassays and the field. Both nematode species were highly infective in the laboratory bioassays. Infectivity was 96 and 94% for S. carpocapsae and H. bacteriophora, respectively. Larvae were extremely susceptible to nematode infection in the laboratory, even in the protected environment inside the crown. Field applications in late fall (October) were less effective with S. carpocapsae and H. bacteriophora resulting in 51 and 33% infection, respectively. Soil temperature was below optimum for both nematode species for the majority of the post application period. Larval mortality was significantly greater in nematode treatments than the control, but nematode treatments were substantially less efficacious in the field than in the laboratory. It is clear from laboratory data, that strawberry crown moth larvae are extremely susceptible to nematode infection. Improved control in the field is likely if nematode applications are made in late summer to early fall when larvae are present in the soil and soil temperatures are more favorable for nematode infection.