Efficacy of two strains of Steinernema feltiae (Filipjev) (Rhabditida: Steinernematidae) against third-stage larvae of common cockchafer (Melolontha melolontha [L.], Coleoptera, Scarabaeidae) under laboratory conditions

In a laboratory experiment an efficacy of entomopathogenic nematode Steinernema feltiae in controlling third-stage larvae of common cockchafer (Melolontha melolontha) was studied. The experiment comprised of commercial product Entonem and indigenous strain C76. The efficacy of both biological agents was tested at 20 and 25 oC and at four different concentrations of nematode suspension: 0, 250.000 infective juveniles [IJs]/m, 500.000 IJs/m, and 1.000.000 IJs/m. Higher mortality rate (27 %) of white grubs was obtained for strain C76 rather than for commercial product (20 %). In our experiment temperature proved to be the most limiting factor in efficacy of tested biological agents. Meanwhile, mortality rate at 20 oC was 34 % and only 12 % mortality was achieved at 25 oC. At highest concentration of nematode suspension and 20 oC also the highest mortality rate (53 %) with strain C76 was obtained.