Lethality of four species of Phasmarhabditis (Nematoda: Rhabditidae) to the invasive slug, Deroceras reticulatum (Gastropoda: Agriolimacidae) in laboratory infectivity trials

Abstract

Slugs such as Deroceras reticulatum (Müller) are among the most important pests of agricultural production throughout North America. Current control strategies are unreliable and this has resulted in increased interest and research on biological control options using nematodes in the genus Phasmarhabditis which have been recently discovered in the U.S. Herein, the lethality of U.S. strains of P. hermaphrodita (Schneider), P. californica Tandingan De Ley, Holovachov, Mc Donnell, Bert, Paine and De Ley, P. papillosa (Schneider) and an undescribed species of Phasmarhabditis at two inoculation rates were investigated for the first time, against D. reticulatum in laboratory infectivity trials. Our data shows that three of the nematode species (P. hermaphrodita, P. californica and P. papillosa) are lethal to D. reticulatum but the extent of and time to cause complete mortality varied. In terms of slug survival (LT 50) and median percentage slug mortality, P. papillosa demonstrated the most lethality in the trials, and the undescribed species the least. However, before an informed decision can be made on the use of these nematodes as effective and safe biological control agents, there are many additional knowledge gaps that need to be filled. Of particular importance will be comprehensive host range testing that incorporates native gastropod species.