D3383: Worms versus slugs: Phasmarhabditis nematodes (Rhabditida: Rhabditidae) are lethal to the invasive gray garden slug, Deroceras reticulatum (Stylommatophora: Agriolimacidae)

Invasive slugs such as the gray garden slug (Deroceras reticulatum) are among the most important pests of agriculture throughout North America. Current control strategies are unreliable, and have damaging non-target effects. This has resulted in increased research on biological control using nematodes in the genus Phasmarhabditis, which have been recently discovered in Oregon and California. In this study, the lethality of U.S. strains of P. hermaphrodita, P. californica, and P. papillosa at two inoculation rates were investigated for the first time, against D. reticulatum in laboratory infectivity trials. Data show that all three of the nematode species are lethal to D. reticulatum but the extent of and time to cause complete mortality varied. In terms of slug survival (LT 50) and percentage slug mortality (median), P. papillosa demonstrated the most lethality in the trials. Before a decision can be made on the use of these nematodes as safe biological control agents, it will be necessary to fill the many remaining knowledge gaps. Of particular importance will be host range testing with native non pest gastropod species.