Pathogenicity of N. rileyi to important lepidopterous pests in laboratory indicated that the cumulative mortality of larvae increased with the increase in concentration and exposure period. The fungus found to be pathogenic to all the six test insects studied with differential degree of pathogenicity. At the highest concentration (1.2 x 10 8, conidia/l), it caused 86.50 per cent mortality of Spodoptera litura followed by Achoea Janata (57,50%), Cydia ptychora (52.50%), Mythimna separata (30%), Earias vittella (27.50%) and lowest in Gaillaria mellonella (20%) after 10 days of exposure period.