Sawadaea bicornis - The powdery mildew <i>Sawadaea bicornis</i> (Wallr.) Homma growing on a maple leaf. Photographed in Burgruine, Liebenberg, Bezirk Waidhofen an der Thaya, Lower Austria, Austria. © Gerhard Koller (Gerhard) - CC BY-SA 3.0 - Wikimedia Commons