Abstract: Phasmarhabditis hermaphrodita is a slug parasitic nematode commercially available as a slug biopesticide (Nemaslug®) in Europe. Two isolates of a new species of genus Phasmarhabditis, EM434 and DF5056, have been recovered separately from unidentified earthworm species in New York; however, the nature of the association between the nematodes and earthworm hosts remains unknown. This study characterized these two isolates and determined their infectivity on three earthworm species and two invasive slugs. Female and male morphology and morphometrics are typical for Phasmarhabditis. Sequences of the D2-D3 expansion segments of the 28S rRNA and mitochondrial cytochrome c oxidase 1 (COI) genes were identical for both isolates. EM434 and DF5056 at the Nemaslug® recommended dose of 30 IJ/sq cm and at higher 150 IJ/sq cm caused mortality to slugs Deroceras reticulatum and Ambigolimax valentianus and to earthworms Eisenia hortensis and E. fetida but not Lumbricus terrestris.