Abstract: The control of wireworms, the larvae of click beetles (Coleoptera, Elateridae), is problematic due to the lack of pesticides. The entomopathogenic fungus Metarhizium spp. shows an efficacy against wireworms in vitro, but the results in the field vary. Here, two new formulations of Metarhizium brunneum were investigated in a field trial with potatoes. One formulation is a granulate (coated millet grain), the other formulation is a soluble dry product. The combined application of granulate and dry product in the potato rows during planting resulted in the highest efficacy. Further investigations considering the wireworm species composition, wireworm distribution and the amount of colony forming units indicated effects on the efficacy.