Microbial Community Dynamics During Decomposition of Insect Exuviae and Frass in Soil

With the expected growth of insect mass rearing industry, residual streams are set to become increasingly available. However, before these residues can be used as organic amendments, more knowledge of the decomposition dynamics and the associated microbial communities is needed. This study aimed to investigate the decomposition, N-mineralization, and fungal/bacterial community composition over a 16-week incubation period of exuviae and frass from BSF, mealworm, and house cricket in pots containing arable soil. The decomposition of insect residues in litterbags was rapid, with over 50% weight loss observed within two weeks. The release of mineral nitrogen from dispersed insect materials was highest during the initial two weeks, particularly evident in soils treated with exuviae compared to their frass counterparts. Moreover, soil amendment with insect residues enriched chitinolytic soil microbial inhabitants belonging to Gammaproteobacteria, Bacilli, Actinobacteria, and Mortierellomycetes. A comparison of soil amendments with sterilized and non-sterilized mealworm exuviae indicated minimal influence of microbial propagules on the composition of bacterial decomposers, though a notable impact on the fungal community was observed. These findings suggest that amendments with insect residues show promise in enhancing natural biocontrol by stimulating microbial antagonists of plant-pathogenic fungi, thereby presenting a potential tool for integration into soil-borne disease management strategies.