Hyaloperonospora berteroae is a host-specific downy mildew oomycete in the family Peronosporaceae that parasitizes Berteroa species, small white-flowered plants in the mustard family (Brassicaceae). It forms colorless sporangiophores that emerge from stomata to produce spores, causing pale patches on infected leaves. Like other downy mildew pathogens, it is an obligate biotroph that cannot survive without a living host.