New blight-like symptoms in the native moss Bryum argenteum were first found on plants growing in a gutter in Omura, Nagasaki, Japan on June 24,2008. White mycelia and rapeseedsized, brown, spherical sclerotia were observed on the diseased plants. A fungus similar to Sclerotium rolfsii was isolated from the infected parts. The mean optimum temperature for mycelia growth of the isolates on potato sucrose agar medium was 25°C and that for sclerotium formation was 30°C; the mycelial tufts were white to grayish brown, with the main hyphal width ranging from 4.3 - 7.9 μm ; clamp connections were observed. These mycological characters were identical to those of S. rolfsii reported in other plants. The isolates were found to be pathogenic to B. argenteum in an artificial inoculation test, and could be re-isolated. Therefore, Koch' s postulates were satisfied. We proposed that this disease be called southern blight of B. argenteum caused by S. rolfsii.
