Optimum thermal requirements for infectivity and development of an indigenous entomopathogenic nematode, Steinernema thermophilum Ganguly & Singh, 2000

Investigations were initiated to evaluate optimum temperature requirements for infectivity and development of an indigenous entomopathogenic nematode, Steinernema thermophilum Ganguly & Singh, 2000 (IARI-EPNI), under laboratory conditions, using greater wax moth larvae (Galleria mellonella) as insect host. The nematode-inoculated insect larvae were exposed to 5 different temperatures, viz. 10, 20, 25, 30 and 35°C. At 35°C, the larval mortality up to 100% was achieved, within 36 hrs. after inoculation (HAI) while at 25 and 30°C, it occurred within 48 HAI, and at 20°C within 216 HAL. At 10°C, the larval mortality was considerably affected, with only 16% mortality even at 216 HAI i.e. 9 days after inoculation (DAI). The IJs started emerging from the cadaver at 7,6 and 5 DAI at 25, 30 and 35°C, respectively. The emergence continued for 3–5 weeks at 25–35°C, with maximum harvest within 16 DAI at these 3 temperature conditions. The number of infective juveniles (IJs) produced per cadaver was maximum at 30 and 35°C. It has been demonstrated that S. thermophilum can infect and develop at a wide range of temperature (20–35°C), the optimum being 25–35°C, with better performance at 30–35°C. Hence, it may prove to be useful bioagent against insect pests of crops especially in tropical and subtropical parts of the world.