Infectivity of Mediterranean native Entomopathogenic Nematodes (Steinerne ¬matidae and Heterorhabditidae) from natural habitats in relation to temperature.

The infectious activity of 15 Steinernema and Heterorhabditis strains of Entomopathogenic Nematodes (EPNs), belonging to 5 species (Steinernema feltiae, S. affine, S. apuliae, S. ichnusae and H. bacteriophora) collected from natural habitats (meadows, coasts and woods) in Southern Italy was compared in laboratory bioassays against Galleria mellonella larvae. Infectivity was determined by 2 larval mortality rate assays in relation to different temperature values. In the first experiment the percentage of larval mortality was recorded after a 72-hr exposure period to the EPNs Infective Juveniles (IJs) at 6 temperatures between 10 and 35°C, at intervals of 5°C, using IJs in aqueous suspension. The second bioassay was performed to compare the infectivity at 3 relatively low temperature values (6-10-14°C), using IJs in 2 different suspensions (aqueous and gel); the percentage of larval mortality was recorded every 72 hrs for 12 days after exposure to IJs. In the first experiment S. feltiae, S. ichnusae and S. affine strains showed the best performances at temperature values 10, 15, 20 and 25°C, while H. bacteriophora and S. apuliae showed the best results at 30 and 35°C. In the second test S. feltiae, S. ichnusae and S. affine strains demonstrated a better cold-infectivity (at 6-10-14°C) than H. bacteriophora and S. apuliae strains. IJs in the water suspension killed the Galleria larvae quicker than those in the gel. The gel suspension keeps nematodes more safe and active than the water one