Peronosporales

An order of the *Oomycetes containing both saprobic and parasitic fungi, many of which are serious plant pathogens. Its members, which number about 300 species in some 16 genera, are found in damp terrestrial   habitats   and include: Pythium (many species of which cause *damping-off of seedlings); Phytophthora infestans (late blight of potato); Plasmopara, Peronospora, and Bremia (various downy mildews); and Albugo (white blister rusts).