First report of powdery mildew caused by Erysiphe alphitoides on Euonymus japonica in Korea.
Euonymus japonica [E. japonicus], family Celastraceae, is an evergreen shrub native to Korea, China, and Japan that is often used as an ornamental hedge plant. In October 2014, powdery mildew symptoms and signs were observed amphigenously on the leaves of Euonymus japonica in a park in Seoul, Korea. Also, in June 2016, the same symptoms were found on Euonymus japonica plants in a garden in Gwangju, Korea, showing higher incidence and severity. Diseased leaves showed white colonies, associated with brown spots on the surface due to the presence of a hyperparasite, Ampelomyces quisqualis, and heavily infected young leaves. Based on morphological characteristics, molecular data (sequence comparison and phylogenetic analysis) and pathogenicity, the causal agent was identified as Erysiphe alphitoides. This is thought to be the first report of powdery mildew caused by Erysiphe alphitoides on Euonymus japonica in Korea and in the world.