Abstract: The solid culture conditions were optimized using single factor experiment, with the aim to improve the conidium production of a strain of Nomuraea rileyi (Nr19) that was determined to be pathogenic to Spodoptera litura larvae. The results showed that the mixture of soybean and wheat bran is a good fermentation medium for Nr19 and significant increase of yields could be achieved with adequate addition of the mixture bran. Control of stage-specific temperature and relative humidity influenced the culture process as well. The optimized conditions were:soybean:bran=85:15, spawn age=5 d, inoculum=15.0%, photoperiod=24L:0D, relative humidity=85% in first 3 d and 60% thereafter, temperature=25℃ in the first 2 d and 28℃ for 3 d and then 25℃ for the last 11 d. Under this optimal fermentation conditions, the highest yields of spore reached (6.045±0.061)×10⁹ conidia/g, which was nearly three folds of that with the un-optimized conditions, and the conidia viability was (93.770±0.278)%. These results can provide practical and experimental supports for further research on preparation of biocontrol agents.

Key words: Nomuraea rileyi, solid culture condition optimization, temperature and humidity, yields of spore, conidial viability