Occurrence of Steinernema species in cabbage fields and the effect of inoculated S. feltiae on Delia radicum and its parasitoids

Abstract 1 Seven organically grown cabbage fields were surveyed for entomopathogenic nematodes in the autumn by baiting. Nematodes were obtained from three fields with bait larvae infection ranging from 1.3–4.0%. 2 Inoculation of Steinernema feltiae (Rhabditida: Steinernematidae) in the spring increased bait larvae infection to 16.0–32.0%. 3 Four different species were found (Steinernema affine, Steinernema bicornutum, S. feltiae and Steinernema C1). 4 The number of Delia radicum (L.) (Diptera: Anthomyiidae) puparia was significantly reduced at plants where S. feltiae had been inoculated. 5 Delia radicum parasitoids were also affected by S. feltiae. The results indicated that Aleochara species (Coleoptera: Staphylinidae) were more negatively affected than Trypliographa rapae (Westw.) (Hymenoptera: Cynipidae).