Metarhizium brunneum is endemic in insect pest populations and fulfils the key criteria as biological control agent: effectiveness, auto-dissemination and persistence. In this three-year field study the influence of the applied entomopathogenic fungus M. brunneum BIPESCO 5 on indigenous Metarhizium species in maize field soils was investigated. The successful mass application of BIPESCO 5 was demonstrated by assessing Metarhizium density (CFU), Metarhizium genotype diversity and their change within the study period. Metarhizium CFU as well as percentage of the recovery of the applied strain BIPESCO 5 increased after periodic applications in spring. Nevertheless, the total number of Metarhizium genotypes in the soil habitat did not change throughout the observation period. No correlation could be observed between increase of BIPESCO 5 and decrease of the number of different Metarhizium genotypes.