First Report of Powdery Mildew Caused by Golovinomyces ambrosiae on the Invasive Weed Symphyotrichum subulatum in Korea

Since the 1980s, an invasive plant, Symphyotrichum subulatum, has become widely naturalized in Korea, competing with native plants and disrupting ecosystems. Since powdery mildew symptoms were initially observed on S. subulatum on a riverside in Busan in 2007, infected plants have been continuously observed. Morphological examination and phylogenetic analysis confirmed Golovinomyces ambrosiae as the causal agent. This study reports the first occurrence of powdery mildew caused by G. ambrosiae on S. subulatum in Korea. Given that this pathogen completes its life cycle by developing its sexual stage in Korea, it poses a potential threat to S. subulatum and other Asteraceae plants.