Powdery mildew
General Powdery mildew is a fungal disease that is caused by many different species of fungi such as Erysiphe, Podosphaera, Oïdium, Leveillula. Damage [...] cultivar how soon after infection this happens. In apple, pear, outdoor grown rose and other Rosaceae , the fungus causing powdery mildew is extremely [...] epidemic is fastest at 18-25 °C. High relative humidity (RH) promotes germination of spores but inhibits spore production, so the net effect of the RH is very