 Other significant Brassicaceous hosts are attacked by different species in the complex, e.g.horseradish ("Armoracia rusticana") by "Hyaloperonospora cochleariae", wallflower ("Erysimum cheiri") by "Hyaloperonospora cheiranthi".Downy mildew is a disease of major importance on the horticultural "Brassica" species.