AbstractDeutzia parviflora var. amurensis is a common ornamental shrub in the Hydrangeaceae. In July and September 2017, powdery mildew infections were first noticed on this shrub in Yichun, China. Powdery mildew colonies on leaves and nonlignified stems were conspicuous, especially when the plants were growing in shade. Based on morphological characteristics and sequencing of the nuclear ribosomal internal transcribed spacer (ITS) region, the pathogen was identified as Erysiphe deutziae. To our knowledge, this is the first report of powdery mildew caused by E. deutziae on Deutzia parviflora var. amurensis in China.