Several novelties of powdery mildews in Japan are reported, including the first Japanese collection of the teleomorph of Erysiphe platani on Platanus × acerifolia, the first description of ascomata of E. viburni on Viburnum sieboldii var. obovatifolium, and the first morphological descriptions and molecular data for E. wallrothii on Leucothoë grayana and Pseudoidium hortensiae on Hydrangea serrata var. megacarpa based on Japanese specimens.