Erysiphe betae is a fungus that causes powdery mildew on various plants, including chard. This fungus is an obligate parasite that forms a layer of white superficial mycelium on the leaves, stems and sometimes on the flowers of the host plant. E. betae spores, called conidia, are dispersed primarily by wind. These spores germinate in conditions of high humidity and moderate temperatures, forming appressoria that penetrate the epidermal cells of the plant. During its growth, the fungus produces more spores that are released into the environment, perpetuating the infection cycle. E. betae can also form resistance structures called cleistothecia that allow its survival in infected plant remains during winter or unfavorable periods.