Desiccation Stress Tolerance of Steinernema Australe and Heterorhabditis Bacteriophora

South African entomopathogenic nematodes (EPNs), Steinernema australe and Heterorhabditis bacteriophora were used for studying the responses of infective juveniles (IJs) to soil desiccation and soil rehydration. The capacity to infect larvae of Galleria mellonella was used to assess the viability of EPNs after their exposure to desiccation. All the samples were initially hydrated to 10% moisture and moisture loss was recorded daily before rehydrating the soil. Desiccation tolerance results revealed that both species were able to withstand desiccated conditions or continuous dehydration for 20 days in sandy loam soil. H. bacteriophora caused 80% larval mortality after day 15 on rehydration of soil, whereas S. australe caused only 60% larval mortality. All the controls, with coarse river sand, gave zero larval mortality by day 21, indicating that the soil texture is also important for EPNs recovery from dehydrated soils. It may be concluded that coarse sand is not ideal for survival and effectiveness of EPNs, because of its incompetence to retain water.