ABSTRACT
In July 2001, a destructive stem rot of tatarian aster (Aster tataricus) was occurred sporadically in exhibition farm of Gyeongsangnam-do Agricultural Research and Extension Services, in Hamyang, Korea. The fungus also caused collar and crown rot and systemic wilt or blight of whole plant. White mycelium spread over stems and petioles of infected plants and sclerotia formed on the old lesions and near the soil surface. The fungus showed maximum mycelial growth was obtained around 30degrees C but did not grow below 5degrees C or above 45degrees C. The mycelial width ranges 4.2~10.4 microm. and the color is white, usually many narrow mycelial stand grow in the aerial mycelium and formed clamp connection. Numerous sclerotia were formed in artificial media like PDA at 30degrees C. The shape of sclerotia were sphere and 1.0~3.2microm in diameter. The fungus was isolated repeatedly from the infected tissues and confirmed its pathogenecity to aster and identified as Sclerotium rolfsii. This is the first report that Sclerotium rolfsii causes stem rot of tatarian aster in Korea.