The Rhododendron powdery mildew fungus Erysiphe izuensis has been recorded throughout Asia, including China, Japan, Korea, and Russia. In Korea, E. izuensis has been identified based on morphological characteristics of the anamorph found on introduced Rhododendron spp. We here describe the first identification of E. izuensis collected from Rhododendron yedoense f. poukhanense in Korea. Morphological characteristics of the teleomorph as well as internal transcribed spacer sequences of the species are provided. Moreover, we describe the characteristics of the primary conidia and conidial surface pattern of E. izuensis for the first time.