Pathogenicity and Host Range of Beauveria nr. bassiana, a Fungal Pathogen of Chilo infuscatellus Snellen

Second and third Instar larvae of the shoot borer Chilo infuscatellus Snell., were more susceptible (51.47 to 65.2 %) to the fungus, Beauveria nr. bassiana even at a low dosage (10⁵ or 10⁶ spores/ml), At 10⁷ spores/ml, the mortality observed was 68.53-75.93 %. Mortality of the larvae decreased with increase in larval age or decrease in the concentration of the fungus. The fungus took less time to cause mortality in second instar larvae and the incubation period Increased with Increase in the age of the larvae or decrease in the dosage. All the six species of phytophagous insects tested Viz., Chilo sacchariphagus indicus (Kapur), C. partellus Swinhoe, Scirpophaga excerptalis Walker, Sesamia inferens Walker, Heliothis arniigera Hubner and Spodoptera litura Fabricius were susceptible to the fungal Infection. The mean mortailty of third Instar larvae varied from 50.0 to 65.0 per cent in the different species. The fungus was not infective to Sturmiopsis inferens Tns. the principal larval parasite of the shoot borer.