The two leaf troubles are respectively known as blight or downy mildew and the Macrosporium disease.
downy mildew spreads and does most damage in hot wet weather.
downy mildew is a fungous trouble affecting the leaves and destroying the further usefulness of the vine.
Practice clean cultivation from the very beginning in order to help control black rot and 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.