In small containers of soil in the laboratory, the enchytraeid Enchytraeus crypticus destroyed colonies of the nematophagous fungus Hirsutella rhossiliensis growing from pelletized hyphae, and reduced biological control of the root-knot nematode Meloidogyne javanica. The enchytraeid also reduced the population densities of the nematode-trapping fungi Monacrosporium gephyropagum, Arthrobotrys thaumasia, and A. haptotyla. Because addition of pelletized hyphae caused rapid and large increases in numbers of E. crypticus, the enchytraeid apparently interfered with biological control by ingesting and consuming the fungi.