The release of large quantities of microorganisms to soil for purposes such as pest control or plant growth promotion may
affect the indigenous soil microbial communities. In our study, we investigated potential effects of Metarhizium brunneum
ART2825 on soil fungi and prokaryota in bulk soil using high-throughput sequencing of ribosomal markers. Different
formulations of this strain, and combinations of the fungus with garlic as efficacy-enhancing agent, were tested over 4
months in a pot and a field experiment carried out for biological control of Agriotes spp. in potatoes. A biocontrol effect was
observed only in the pot experiment, i.e. the application of FCBK resulted in 77% efficacy. Colony counts combined with
genotyping and marker sequence abundance confirmed the successful establishment of the applied strain. Only the
formulated applied strain caused small shifts in fungal communities in the pot experiment. Treatment effects were in the
same range as the effects caused by barley kernels, the carrier of the FCBK formulation and temporal effects. Garlic
treatments and time affected prokaryotic communities. In the field experiment, only spatial differences affected fungal and
prokaryotic communities. Our findings suggest that M. brunneum may not adversely affect soil microbial communities.