Response of native entomopathogenic nematode, Steinernema spp. (TFRIEPN-57) isolated from central India to variation in temperature and soil moisture

摘要

The paper reports effect of temperature and soil moisture on horizontal or vertical dispersal by infective juveniles (IJs) of native entomopathogenic isolate, Steinernema sp. (TFRIEPN-57) from central India. The observations recorded 72 hrs after exposure of IJs to eleven temperature regimes (0, 5, 10, 15, 27, 30, 32, 34, 36, 38 and 40 degrees C) revealed survival of IJs from 10 to 36 degrees C temperature, below and above which, there was 100% mortality. Within the above range, IJs exposed to 10 degrees C. and 36 degrees C showed 88.59% and 55.41% survival, respectively. Exposure of Us to 0 degrees C revealed no survival at and above 12 hrs, whereas 5 degrees C allowed survival up to 48 hrs. Us exposed to temperature extreme of 38 degrees C exhibited 38.98% survival up to 8 hrs. Soil moisture of 10% proved suitable for horizontal dispersal of IJs towards the G. mellonella larvae embedded in soil 30 cm away from the point of release in 72 hrs. There was no horizontal dispersal beyond 30cm. However, the Us exposed to soil moisture of 10 and 15% displayed vertical dispersal up to 40 cm towards embedded G. mellonella larvae in 72 hrs. Multiple regression analysis of the data showed that infectivity in embedded G. mellonella larvae at various horizontal and vertical distances from the point of release of IJs had significant positive correlation with soil moisture and exposure time and significant negative correlation with distance.