Susceptibility of the cutworm, Agrotis segetum (Lepidoptera: Noctuidae) to entomopathogenic nematodes

Abstract: The cutworm, Agrotis segetum Schiff. (Lepidoptera: Noctuidae) is a species widely spread in Europe that damages the cultivated plants belonging to more than 15 families and including host plants such as okra, cabbage, cauliflower, rutabaga, bell pepper, tomato, potato, maize and cotton. The effect of entomopathogenic nematodes (EPNs), Heterorhabditis bacteriophora and a new species from Georgia, Steinernema thesami was investigated in the last instar of cutworm larvae and pupae in the laboratory conditions. The nematodes were used in the following doses: 50 and 100 infective juveniles (IJs) per insect. The mortality of tested insects was estimated on the third day after the EPN application. The last instar of larvae turned out to be more susceptible in the course of laboratory experiments. No significant differences were observed between H. bacteriophora and S. thesami at a low concentration of 50 IJs per insect during all exposure times, whereas S. thesami was more pathogenic against larvae at a high concentration of 100 IJs per insect as compared with H. bacteriophora and the mortality reached 97.2-100%. The emerging IJs were harvested and counted throughout the interval of 11-15 days. The experiments were carried out in the laboratory conditions at a temperature of 22 °C and 80% RH.