Powdery mildew
apple, pear, outdoor grown rose and other Rosaceae , the fungus causing powdery mildew is extremely sensitive to water and ‘hides’ on the underside of the [...] mildew fungi and especially in greenhouse crops they don’t play a role in the epidemics. Fungal spores germinate on the leaf surface and the germ tubes [...] tubes grow and branch out on the leaf surface. Small structures are produced, the haustoria, from which the fungus penetrates the plant cell and takes up nutrients