Effects of crop residue on the persistence of Steinernema carpocapsae

We determined the effects of crop residue on the persistence of an entomopa thogenic nematode, Steinernema carpocapsae. During 2 consecutive years, nem atodes were applied at rates of 2.5 x 10(4) and 1.0 x 10(5) infective juven iles/m(2) to small field plots planted with corn. Nematode persistence was monitored by exposing Galleria mellonella larvae to soil samples from plots with and without crop residue (approximately 75% coverage of soybean stubb le). Persistence of S. carpocapsae was significantly greater in crop residu e plots than in plots without residue. In crop residue plots that received the higher rate of nematode application, larval mortality did not significa ntly decrease during the study period (3 to 5 days) and remained above 85%. In nematode-treated plots without crop residue, however, larval mortality fell from over 96% to below 11% and 35% in the first and second trials, res pectively. The increased crop residue may have benefited nematode persisten ce through protection from desiccation or ultraviolet light. We conclude th at increased ground cover in cropping systems (e.g., due to reduced tillage ) may lend to increased insect pest suppression with entomopathogenic nemat odes.