First report of powdery mildew caused by Erysiphe alphitoides on Euonymus japonicas and its natural teleomorph stage in China.
In summer 2015, symptoms of severe powdery mildew were observed on ∼80% of Euonymus japonicus plants grown in the gardens of Qingdao (Shandong, China). White mycelial growth was found on both sides of the leaves, which caused them to discolor and crinkle. Conidia formed singly and were ellipsoidal or cylindrical without distinct fibrosin bodies. Based on morphological characteristics, molecular data (sequence comparison and phylogenetic analysis) and pathogenicity tests, the causal agent was identified as Erysiphe alphitoides. This fungus is a worldwide pathogen that causes powdery mildew on oak trees. However, this is thought to be the first report of Erysiphe alphitoides infecting Euonymus japonicus in China, with observations on its teleomorph stage. The presence of powdery mildew on Euonymus japonicus detracts from the esthetic value of these plants, and in some instances resulting in death and severe yield reduction.