Insects are among the most diverse and abundant organisms on Earth, and their population dynamics are strongly influenced by entomopathogenic fungi. This study examines the role of carbon and nitrogen metabolism in the virulence of the entomopathogenic fungus Metarhizium rileyi against the migratory locust, Locusta migratoria. The findings demonstrate that the capacity of M. rileyi to utilize different carbon and nitrogen sources is a key factor in its virulence. Specifically, two strains of M. rileyi (PPDB201006 and SZCY201010) exhibited distinct metabolic abilities, with PPDB201006 displaying superior growth and enzyme activities on various carbon and nitrogen sources compared to SZCY201010. These metabolic differences were associated with significant variations in virulence, as PPDB201006 induced higher mortality rates in L. migratoria than SZCY201010. Metabolomics analysis revealed that infection by M. rileyi led to substantial alterations in the hemolymph metabolites of L. migratoria, particularly in organic acids, amino acids, sugars, and lipids. These results emphasize the significance of carbon and nitrogen metabolism in the pathogenicity of entomopathogenic fungi and offer new perspectives for optimizing their application as biological control agents. This study not only improves our understanding of fungal virulence mechanisms but also contributes to the development of more effective and sustainable pest management strategies.

Bombyx batryticatus is a traditional Chinese medicinal material derived from Bombyx mori infected by Beauveria bassiana; however, its formation mechanism remains poorly understood. This study compared infection processes in silkworms by two B. bassiana strains with markedly different virulence (highly virulent ZY027 and ARSEF2860). Integrated transcriptomic and proteomic analyses were employed to uncover, for the first time, the molecular basis of B. batryticatus formation at the systems biology level. The results demonstrated significant weight variations in B. batryticatus derived from different fungal strains. ZY027-induced stiff silkworms exhibited higher wet and dry weights than those infected by ARSEF2860. Large-scale gene reprogramming occurred in silkworm hemolymph post-infection, involving marked activation of Toll/Imd immune signaling pathways, ribosome biogenesis, and endoplasmic reticulum stress responses. A notable “uncoupling” between transcriptomic and proteomic profiles was identified, highlighting the critical role of post-translational regulation in host responses. The two strains triggered distinct metabolic reprogramming patterns: ZY027 notably suppressed oxidative phosphorylation and activated detoxification mechanisms, whereas ARSEF2860 presented characteristics of “immune–metabolic optimization.” These findings suggest that B. batryticatus formation involves complex fungus–silkworm molecular interactions in hemolymph, and that fungal strain characteristics are associated with significant differences in host molecular responses and product biomass. The study provides a theoretical foundation and innovative guidance for selecting strains with high B. batryticatus production potential and developing novel entomopathogenic fungal resources.