Influence of dry heat, hot water and UV radiation on host infectivity of entomopathogenic nematode, Heterorhabitis indica (Poinar)

Abstract

Entomopathogenic nematodes are considered as potential biocontrol agents of major insect pests of cultivated crops. The lepidopteron pests such as Helicoverpa armigera and Spodoptera litura as well as few coleopterans like Myllocerus spp. and Holotricha sp. are effectively managed by entomopathogenic nematodes. An in vitro experiment was conducted to enhance the efficacy of Heterorhabditis indica using physical stressors. Physical stressors viz., dry heat, hot water and UV radiation exposure were used in this experiment. These stressors were imposed on final instar larvae of rice moth, Corcyra cephalonica. The results showed that exposure of C. cephalonica larvae to 35°C dry heat for 10 minutes increased the infection rate to an extend of 10 per cent more compared to control. The infection rate of H. indica was also influenced by exposure of insect larvae to hot water. Out of four temperatures tested, immersion of insect larvae in hot water at 40°C for 10 minutes showed an increase in infection rate (51% increase over control). There was no significant influence on infectivity rate of H.indica due to UV radiation exposure.