Effect of Soil Moisture and Ultraviolet Radiation on the Activity of Entomopathogenic Nematodes

Entomopathogenic nematodes are not effective at high temperature; sensitive to ultraviolet light and require adequate moisture and high relative humidity for survival for reasonable length of time. The present study investigated the impact of soil moisture and ultraviolet (UV) radiation on the virulence of the entomopathogenic nematodes viz., Heterorhabditis indica and Steinernema glaseri. The levels of soil moisture at 3 to 25% and UV radiation at 30 to 210 minutes were tested under laboratory conditions. The survival and infectivity of entomopathogenic nematodes in insect host were studied. The survival of H. indica and S. glaseri was observed at 4 and 5% soil moisture respectively. The last instar larvae of Corcyra cephalonica showed 100% mortality at 14 to 25% soil moisture for H. indica and 16 to 25% soil moisture for S. glaseri. Ultraviolet light emitted from a UVlamp of 15W caused 100 per cent mortality of H. indica and S. glaseri after 120 and 210 minutes, respectively indicating both are sensitive to UV light. The infective juveniles exposed to UV light were failed to infect C. cephalonica.