The powdery mildew on Castanea crenata in South Korea was first recorded as Microsphaera
alni in 1958. On the basis of its morphological characteristics and host range, the mildew was
determined as Microsphaera sinensis in 1988. According to the rules of The International Code
of Botanical Nomenclature, M. sinensis was renamed Erysiphe castaneigena in 2006.
Nevertheless, taxonomic re-consideration of the morphological and molecular characteristics
for the Castanea powdery mildew in Korea has not been performed. In the present study, we
studied 34 powdery mildew samples collected from C. crenata in the Korea University
Herbarium. On the basis of microscopic examinations of the holomorph and phylogenetic
analysis of the internal transcribed spacer regions, we confirmed the powdery mildew fungus as
E. castaneigena. In addition, sequence comparison between E. castaneigena and E. alphitoides
ex Castanea sp. suggested a close phylogenetic affinity.