Pieces of monofilament nylon cloth cdlonized by the fungus causing strawberry red core were buried in autoclaved and untreated soil at 3 moisture contents and at 3 deg , 15 deg and 30 deg C. They were recovered at intervals and tested by infection of bait plants and for the production of sporangia when irrigated with calcium nitrate solution. Infectivity persisted longest in autoclaved moist soil held at 3 deg where it was still detectable after burial for 1 yr. It declined most rapidly in untreated soil at 15 deg and 30 deg , not being detectable in any treatment combination after 63 days; the rapid loss of infectivity coincided with the disappearance of mycelium from the material. By contrast, naturally infested soil stored moist at 15 deg remained infective for 8 months. These results demonstrate that the known, long persistence of P. fragariae in field soils cannot be as mycelia but must be by oospores.