Submitted to: American Phytopathological Society Press
Publication Type: Book / Chapter
Publication Acceptance Date: 4/20/2020
Publication Date: N/A
Interpretive Summary: Powdery mildew is a common foliar disease of pea. The disease is caused by Peronospora viciae. The infection could be systemic or local. The pathogen overwinters as thick-walled oospores in the soil, on plant debris, and oospores are believed to be the major or exclusive source of primary inoculum. This chapter describes the distribution, infection types, symptoms and race differentiations of pea downy mildew pathogen, with photographic illustrations to aid disease diagnosis and options for disease management.
Technical Abstract: Downy mildew is one of the serious foliar diseases of peas worldwide. Downy mildew of pea is caused by Peronospora viciae. It is a filamentous fungus-like microorganism, belonging to the oomycetes, in the kingdom Stramenopila. It is a biotrophic parasite. The pathogen overwinters as thick-walled oospores in the soil, on plant debris, and oospores are believed to be the major or exclusive source of primary inoculum. The infection of downy mildew could be systemic or local. Systemically infected plants are stunted with lighter shades of green/yellowish foliage than healthy plants, are distorted, and have shortened internodes. Usually, the whole plant is killed prior to flowering. Local infections can occur on leaves or pods. Eleven races of Peronospora viciae are recognized based on variation of virulence on a set of four differential cultivars. The most economical and environmentally-friendly way to control downy mildew of pea is to plant resistant cultivars. Proper seed treatments can reduce seedborne inoculum and reduce disease pressure. Foliar fungicides are also available for managing downy mildew.