Podosphaera leucotricha - Apple Powdery Mildew (<i>Podosphaera leucotricha</i>) on the Malus in <a href="//commons.wikimedia.org/wiki/File:Apple_blossom_1_-_geograph.org.uk_-_1274740.jpg" title="File:Apple blossom 1 - geograph.org.uk - 1274740.jpg">1274740</a>. The dry conditions of the spring of 2009 have exacerbated this disease. © Jonathan Billinger - CC BY-SA 2.0 - Wikimedia Commons