Field Persistence of \u3ci\u3eSteinernema Carpocapsa\u3c/i\u3e Weiser (Ny001), \u3ci\u3eSteinernema Feltiae\u3c/i\u3e Filipjev (Valko) and \u3ci\u3eHeterorhabditis Bacteriophora\u3c/i\u3e Poinar (Oswego) in Alfalfa Fields

Abstract

The long term field persistence of Steinernema carpocapsae Weiser, strain NY001, S. feltiae Filipjev, strain Valko and Heterorhabditis bacteriophora Poinar, strain Oswego was investigated in an alfalfa field infested by the alfalfa snout beetle, Otiorhynchus ligustici L. Nematodes were applied in single-species, two-species and three-species combinations at a total of 2.5 × 109 infective juveniles per hectare. Soil samples were taken approximately every two weeks from mid/late May to late October in 2004 and 2005. Two soil samplings were conducted in 2006 at the end of May and in early July. All nematodes persisted in the field at the time of the last sampling in July 2006, over two years after application suggesting long term persistence of these nematodes and the potential to coexist in combinations. Steinernema feltiae Valko was not detected in the three-species combination after June 8, 2005, approximately one year after nematode application suggesting that S. feltiae Valko cannot compete effectively when a specialized ambusher nematode (S. carpocapsae NY001) and a specialized cruiser nematode (H. bacteriophora Oswego) are present simultaneously. In 2006, two years after nematode application, a marked movement of nematodes into experimental plots where they were not applied was observed. S. carpocapsae NY001 was found in the highest number of plots where it wasn’t applied. Given the ambusher behavior of S. carpocapsae NY001, it is suspected that its movement occurred via infected, but still live adult alfalfa snout beetles