DESICCATION TOLERANCE OF ALGERIAN STRAINS OF ENTOMOPATHOGENIC NEMATODES

In this study a preliminary contribution to the desiccation tolerance of Algerian entomopathogenic nematodes (EPNs) is reported. Laboratory experiments were performed to assess the survival of 6 Algerian EPN strains upon direct exposure of infective juveniles (IJs) to 2 relative humidities (rh) on membrane filters. The strains were isolated from different biotopes in Algeria and belong to 2 species: Steinernema feltiae (4 strains) and Heterorhabditis bacteriophora (2 strains). IJs were exposed to 84% and 76% rh at similar to 20 degrees C for up to five days, and the percentage of surviving IJs was recorded twice daily. Three replicate desiccators per time interval were used for each nematode strain and the assays were repeated 3 times. Survival decreased as rh decreased and with increasing periods of exposure. The tolerance of these nematodes to dessication was generally high, especially for the H. bacteriophora strains which exhibited the longest survival ability. At 84% rh the H. bacteriophora strains displayed a desiccation tolerance of at least 5 days, with a survival percentage of 26-33%, while the other nematodes yielded a low survival percentage (8-11%) after 5 days. At 76% rh H. bacteriophora again survived for a minimum of 5 days (12-18%) whereas the S. feltiae strains survived for only 3 days (5-10% of surviving IJs). No significant differences in pathogenic activity and ability to penetrate Galleria mellonella larvae were observed between non-desiccated IJs and rehydrated ones for any of the strains.