Factors Influencing Expression of Symptoms in Corcyra cephalonica by Entomopathogenic Nematode, Heterorhabditis indica

Influence of environmental factors on expression of symptoms in Corcyra cephalonica (Rice Moth) larvae infected with Heterorhabditis indica was studied. Good symptom expression was noticed when maximum humidity was above 82%, minimum humidity was above 60%, maximum temperature below 39.7°C and minimum temperature ranged between 23.2- 26.8°C. Humidity was recorded to be the critical factor in expression of symptoms. At minimum humidity of less than 28.5%, number of infected insects expressing symptoms had reduced to zero. Nematode population development and build-up was very poor in symptomless insect larvae. Only secondary colonies of bacterial symbiont Photorhabdus luminescens were obtained from non-symptomatic larvae while larvae showing symptoms yielded more number of primary phage bacterial colonies.