Introduced populations of the north temperate ant species, Myrmica rubra (L.), have become pestiferous in parts of the northeastern U.S., particularly in coastal Maine communities. Surveys of middens associated with nests in both the native and introduced range of this ant, have commonly revealed infections by the entomopathogens, Metarhizium anisopliae and Beauveria bassiana. A number of factors including self- and allogrooming and production of antimicrobial compounds, have been shown to aid social insects in defense against these pathogens. Solenopsis invicta has been shown in other studies to disperse venom with antimycotic activity against these pathogens. We conducted experiments to examine whether soil from M. rubra nests has any residual activity against M. anisopliae. Soil samples were collected from: a) areas actively tunneled and inhabited by ants, and b) areas 1 m from nests and not occupied by ants. Nest soil and non-nest soils were incubated in the laboratory with and without ant colonies, respectively, for 3 weeks. After incubation, all ants were removed, and half of each soil sample was sterilized. A 2 x 2 factorial design was used to test the effect of ant presence and soil sterilization on germination of spores and infection of ants by M. anisopliae. Nest soil (ant presence) was found to have no effect on germination or infection, but soil sterilization did significantly enhance infection. Observed fungistatic and/or fungitoxic effects of the nonsterilized soil is likely mediated by soil microorganisms and appears independent of the presence of ants.