This 2-page factsheet highlights the findings of a project to develop an integrated management strategy for the control of downy mildew on Brassica and stock seedlings, which is caused by the fungus Peronospora parasitica. The disease, which discolours foliage and causes premature defoliation is responsible for substantial losses to seedling growers. The factsheet provides information on the host range (eg broccoli, Brussels sprouts, cabbage, cauliflower and Chinese cabbage), symptoms, the process of infection, how and when it spreads and control strategies, which must consist of both management practices (eg controlled irrigation, ventilation and balanced nutrition) and fungicide spray programs.