Abstract: 【Objective】 The objective of this study is to induce microsclerotia (MS) of Nomuraea rileyi strain CQNr01, and to provide a novel preparation type and production process for insects control with this entomopathogenic fungus.【Method】The CQNr01 was cultured in liquid medium containing special salts solutions and medium components including concentration of carbon, nitrogen and their ratio were optimized. Germination rates of microsclerotia and the pathogenicity in larvae of Spodoptera litura were determined with the dried and preserved microsclerotia.【Result】The MS with cell structural differentiated and pigmentation was induced successfully under the optimized cultural conditions. The MS yield was affected by carbon concentrations and carbon-to-nitrogen ratios. Within a certain point the medium with lower carbon concentrations produced more MS at same carbon-to-nitrogen ratio. Microsclerotial granules of N. rileyi CQNr01 were siccostabile. The microsclerotia mixed with diatomite, air-dried and kept in storage for 6 month had no signi?cant loss in viability. After rehydrating and incubating in water agar plates, MS could germinate and produce conidia. Bioassays results showed that the dried MS preparations can infect the larvae of S. litura and the corrected mortality was 78.56% in 14 d after inoculation. The LT50 was about 7 d at the tested dosage. 【Conclusion】Microsclerotia of N. rileyi CQNr01 can be induced by specific medium components in liquid culture. The induced microsclerotia remain activity and keep high infective ability to kill insects. The microsclerotia might be used as the potential bio-pesticide agent for insect biological control.

Key words: microsclerotia, Nomuraea rileyi, biocontrol agent, Spodoptera litura