downy-mildew (Plasmopara viticola) rivals black-rot for first place among fungous diseases of the grape.
downy-mildew, like black-rot, spreads most rapidly and does most injury in hot, wet weather.
The berries, however, do not become soft and shrunken as when attacked by the downy-mildew.
|downy mildew |
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.