First Report of Frosty Mildew on Salix koreensis Caused by Mycopappus alni in Korea

A frosty mildew was observed on leaves of Salix koreensis in two localities of Korea during 2011 and 2012. The main signs and symptoms were expressed as conical white to cream coloured tufts of the causal fungus on the brown lesions, followed by premature defoliation. Based on morphological observations, cultural characteristics and phylogenetic analyses of rDNA‐ITS, the fungus was identified as Mycopappus alni, which has been known to be associated with frosty mildews on Alnus spp., Betula spp., Crataegus chlorosarca and Pyrus pyrifolia. Pathogenicity test was conducted twice with the same results, fulfilling Koch's postulates. This is the first case of Salix–Mycopappus association as well as the first report of frosty mildew on S. koreensis.