Metarhizium anisopliae, the entomopathogenous fungus causing the green muscardine disease is known to induce a high mortality of the eastern subterranean termite Reticulitermes flavipes in laboratory conditions. However, there is no definitive evidence showing that this fungus is a successful biological control agent against field populations of termites. Contrary to previous lab studies in which termites were typically tested in Petri dishes, the effect of M. anisopliae on R. flavipes was studied in a two-dimensional arena where the termites were allowed to forage in soil. Our results suggested that no epizootic occurred in this bioassay that was designed to simulate field conditions. Moreover, only 4% of the introduced fungal conidia survived after 3 months of experiments suggesting that the termites had an efficient defensive mechanism against this pathogen.