Pseudoperonospora urticae is an obligate biotrophic oomycete downy mildew pathogen in the family Peronosporaceae, infecting stinging nettle (Urtica) species. It causes yellowing and chlorosis of leaves with characteristic grayish sporulation on the undersurface during moist conditions. Its host specificity to nettles makes it an interesting model for studying coevolution between oomycete pathogens and their wild hosts.