Abstract: Two species of fungi, Beauveria bassiana (Bals.-Criv.) Vuill. and Beauveria brongniartii (Saccardo) Petch were jointly applied in the field as biological agents in strawberry plantations in Poland to control Melolontha melolontha L. (European cockchafer). We adapted a genotyping approach based on SSR (Simple Sequence Repeat) marker to a discriminating tracing of the two inoculants in vitro and in soil. We analysed the behaviour of the two fungal species in vitro in the presence of different carbon sources, to assess possible antagonistic and/or synergistic effects of the consortium. Further, we used SSR markers in the assessment of inoculants persistence and traceability in soil after their field application.