Pathogenicity of Rhabditid nematodes (Nematoda: Heterorhabditidae and Steinernematidae) to alfalfa snout beetle (Coleoptera: Curculionidae) larvae

Three naturally occurring entomopathogenic nematodes--Heterorhabditis bacteriophora Poinar (Oswego strain), Steinernema carpocapsae (Weiser) (NY001 strain), and Steinernema sp. (undescribed) (NY008-2E strain)--and four nematodes obtained from commercial sources-H. bacteriophora (NC strain), Steinernema feltiae N-356 strain), Steinernema riobravus. (355) strain, and Steinernema glaseri (326 strain)-were tested for pathogenicity against alfalfa snout beetle larvae, Otiorhynchus ligustici (L.) In laboratory bioassays using soil, all nematodes except H. bacteriophora (Oswego strain) caused 50% mortality in mature alfalfa snout beetle larvae exposed to 200 infective juveniles. At a similar rate H. bacteriophora (Oswego strain) caused 65-80% mortality in mature alfalfa snout beetle; larvae. In the greenhouse, H. bacteriophora (Oswego strain) killed 90% of alfalfa snout beetle larvae infesting potted alfalfa plants 14 d after application of 30,000 infective juveniles to the soil surface. Application of 4,500 infective juveniles of H. bacteriophora (Oswego strain) to pots containing alfalfa infested with alfalfa snout beetle larvae significantly reduced feeding damage to roots by alfalfa snout beetle larvae and subsequently preserved the dry weight of the roots. Results from these laboratory bioassays and studies with potted plants in greenhouses suggest that entomopathogenic nematodes, particularly H. bacteriophora (Oswego strain), deserve further study as potential biological control agents against alfalfa snout beetle larvae infesting alfalfa fields in New York