Chiang Mai Journal of Science

     Leaves of Caesar weed (Urena lobata) with typical powdery mildew symptoms were collected from Baiyun Mountain Park in Guangzhou, China during winter and summer in 2020 and 2021. Based on the morphology and molecular sequence analyses of Internal Transcribed Spacer (ITS) and large subunit (LSU) rDNA region, the causative agent was identified as Erysiphe quercicola. A description and relevant microscopic images of the pathogen are provided. According to our knowledge, this is the first report of E. quercicola on Urena lobata and this study expands the host range of E. quercicola. Further, we provided details of life cycle and geographical distribution of the fungus.