Effect of entomopathogenic fungus Beauveria bassiana on the growth characteristics and metabolism of black soldier fly larvae

Beauveria bassiana is an entomopathogenic fungus widely used in agriculture to reduce populations of various pests. However, when agricultural waste is utilized for organic recycling, B. bassiana has the potential to impact recycling performance, by affecting the survival, and body mass of decomposing organisms (such as insect's larvae). Additionally, in natural conditions where decayed organic matter contains a high load of different entomopathogenic organisms, larval growth may be affected when consumed or in contact. In a laboratory study, we aimed to comprehend the effects of B. bassiana on the growth characteristics and larval metabolism of the black soldier fly larvae, which is a known decomposing insect. The experiments used both feeding (mixing the spores with the diet, hereafter BF) and contact treatments (by dipping the larva in the spores solution, hereafter BD), and were compared to a water-treated control group. The BF treatment significantly reduced larval body weight, adult emergence, and adult weight compared to both the control and the BD treatment. Furthermore, an analysis of hemolymph metabolites, categorized by class, indicated a higher accumulation of metabolites belonging to the purine and purine derivative classes, as well as carboxylic acids and their derivatives, including peptides and oligopeptides, indicating potential disruption of protein synthesis or degradation caused by the BF treatment. Pathway enrichment analysis showed significant alterations in purine metabolism and D-Arginine and D-ornithine metabolism compared to the control. Taurine and hypotaurine metabolism were significantly altered in the BD treatment compared to the control but not significantly enriched in the BF treatment. Our results suggest that the BF treatment impairs protein synthesis or degradation, affecting larval growth characteristics. Future studies should explore innate immunity-related gene expression and antimicrobial peptide production in BSF larvae to understand their immunity to pathogens.