Discovery of Phasmarhabditis hermaphrodita (Rhabditida: Rhabditidae) in the United States and its potential as a biological control agent of pest gastropods

The nematode Phasmarhabditis hermaphrodita (Rhabditida: Rhabditidae) was commercialized as Nemaslug® in 1994 in the United Kingdom. Over the past 30 years, this product has been used by growers in fifteen European countries to manage pest slugs and snails in a wide range of crops. Phasmarhabditis hermaphrodita was discovered for the first time in North America in California in 2014 and was subsequently collected in Oregon (2017). These discoveries have led to increased interest in the potential use of P. hermaphrodita as a biological control agent of pest gastropods in the United States. Laboratory infection trials have demonstrated that the U.S. strain is lethal to many of the key slug and snail pests in the region including the highly damaging species, Deroceras reticulatum (Stylommatophora: Agriolimacidae) and Cornu aspersum (Stylommatophora: Helicidae). Furthermore, in microcosm studies, the U.S. strain caused significantly higher D. reticulatum mortality than a commonly used slug bait (Slug-Fest®) and the negative control for much of the study. However, non-target assays with the native snail, Monadenia fidelis (Stylommatophora: Xanthonychidae) demonstrated that P. hermaphrodita caused significantly higher mortality to this non-pest species than the negative control, thus raising questions about the safety of using P. hermaphrodita as a biological control agent in the U.S. Future research directions for this and other Phasmarhabditis nematodes are proposed.