- Also called false mildew. any fungus of the family Peronosporaceae, causing many plant diseases and producing a white, downy mass of conidiophores, usually on the under surface of the leaves of the host plant.
- Plant Pathology. a disease of plants, characterized by mildewed, distorted, and yellowed foliage, caused by any of several fungi of the family Peronosporaceae, as of the genera Peronospora and Phytophthora.
Origin of downy mildew
First recorded in 1885–90
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for downy mildew
Downy-mildew, like black-rot, spreads most rapidly and does most injury in hot, wet weather.
Downy-mildew (Plasmopara viticola) rivals black-rot for first place among fungous diseases of the grape.
The berries, however, do not become soft and shrunken as when attacked by the downy-mildew.
- a serious plant disease, characterized by yellowish patches on the undersurface of the leaves, caused by the parasitic fungi of the family Peronosporaceae, such as Peronospora destructor: affects onions, cauliflower, lettuce, etc
- any of the fungi causing this disease
Compare powdery mildew
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
- A disease of plants caused by oomycete organisms of the order Peronosporales and characterized by gray, velvety patches of spores on the lower surfaces of leaves. Downy mildew of the grapevine nearly destroyed the French wine industry in the 1870s, spurring the development of the first chemical pesticides used on plants.
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