Effect of temperature on the pathogenicity of mediterranean native entomopathogenic nematodes (steinernematidae and heterorhabditidae) from natural ecosystems

Seven strains of entomopathogenic nematodes (EPNs) belonging to three species (Steinernema feltiae, S. ichnusae and Heterorhabditis bacteriophora) naturally isolated from Mediterranean countries (Southern Italy and Lebanon) were evaluated for their potential to infest greater wax moth (Galleria mellonella) larvae at different temperatures under laboratory conditions. The laboratory bioassay was conducted at six different temperatures ranging from 10°C to 35°C. Nematode Infective Juvenile (IJs) were put in contact with G. mellonella larvae in Petri dishes and mortality rates were recorded after 72 hours. The purpose of the study was to evaluate the temperature range in which the EPNs caused larval mortality; higher mortalities were recorded at 15°C and 20°C. All species failed at lower temperatures except for S. ichnusae ItS-SAR4, which caused 7% mortality. At 35°C S. ichnusae maintained its infectious activity (24%) along with H. bacteriophora ItH-LU1 (38%); both were isolated from Italy and were more efficient at high temperatures than the remaining Lebanese isolates.