Entomopathogenic nematodes (EPNs) in families Heterorhabditidae and Steinernematidae have considerable potential as biological control agents against soil-inhabiting insect pests. In the present study, the potential of Steinernema feltiae as a biological control agent against cabbage maggot (CM) Delia radicum (Diptera: Anthomyiidae), persistence of the nematode in areas infested by CM larvae, and foraging behavior of the nematode toward CM and/or oilseed rape roots were examined in the laboratory. The results of the laboratory experiment showed that more than 80% control was achieved against the last instars of D. radicum. Steinernema feltiae persisted in the soil in high numbers for 12 weeks in laboratory assays. The foraging behavior of S. feltiae in the presence of D. radicum larvae and oilseed rape roots, offered individually and in combination, was studied using a Y-tube olfactometer filled with silver sand (Humax. U.K., particle size: 300-400 mu m) at 8 and 15 degrees C. When insect larvae were present, more nematodes migrated toward the larvae at both temperatures.