Aims: To investigate the nutritional requirements of the mycelial growth and pathogenesis-related enzymatic activity on Isaria farinosa and the nutritional effect of fungus on its host Hepialus larvae. Methods and Results: Sixteen carbon sources, 16 nitrogen sources and 9 vitamin combinations were tested. The nutritional conditions that significantly prevented I. farinosa pathogenesis were selected as feed additives for rearing Hepialus larvae. Citric acid significantly inhibited the growth of I. farinosa and the activity of three enzymes. L-histidine and L-aspartic acid significantly reduced the dry weights of mycelia and their protease and lipase activities. Vitamin combination that lacked VB1 significantly increased the growth of I. farinosa and enhanced its chitinase and lipase activities. L-aspartic acid, VB1 or a combination of them were beneficial for maintaining the larvae survival rate and decreasing the disease rate. The result provides new insight to develop a nutrition-based strategy to control fungal epidemics during insect rearing. Conclusions: The ability of some specific nutrients to inhibit mycelial growth and enzymatic activity can prevent epidemics of fungal disease. Significance and Impact of the Study: These results will aid in the development of nutrition-based strategies to control entomopathogenic fungal epidemics during the large-scale rearing of insects.