remain dormant all winter to germinate in spring. When the asci expand they rupture the cleistothecia wall, throwing the ascospores into the air. Ecology Erysiphales are obligate parasites on leaves and fruits of higher plants, causing diseases called powdery mildews. Most attempts to grow them in culture have failed. Erysiphales have a nearly cosmopolitan distribution, except Australia, and have developed fungicide resistance just as widely. Total loss of function has resulted in some cases. Resistance management planning, use of multi-mode of action fungicides, and altered frequency and quantity of application are needed to slow the progress of resistance. Genera Arthrocladiella Blumeria Brasiliomyces Bulbomicrosphaera Bulbouncinula Caespitotheca Cystotheca Erysiphe (Oidium) Golovinomyces Leveillula (Oidiopsis) Medusosphaera Microsphaera Neoerysiphe Oidium Phyllactinia (Ovulariopsis) Pleochaeta Podosphaera Sawadaea Setoerysiphe Sphaerotheca Typhulochaeta Uncinula Uncinuliella References A University of Winnipeg page on Erysiphales Key to common genera (4 megabyte file) Fungal plant pathogens and diseases Ascomycota orders Monotypic fungus taxa Taxa named by Edmond Tulasne