4. 
and when it is sufficiently developed to produce spores it breaks 
through the lower surface of the leaf in such patches as have been 
described. Microscopic white threads project from the leaf and bear 
the summer spores of the fungus. It is this condition which gives 
the disease the name of Downy Mildew. These white patches are 
more easily found upon varieties of grapes which have smooth leaves, 
like the Clinton and Delaware, because the cottony under surface 
of the leaves of the Concord type makes the downy patch less con- 
spicuous. 
On the canes this disease causes brown spots, slightly depressed. 
They are not as deep as those caused by anthracnose and not so 
dark. The evidence is not so frequently found upon the stem as upon 
the leaves. 
When the berries are attacked, usually while small, they are 
checked in their development and do not gain full size. They turn 
brown or, if the fungus is fruiting upon it, the surface appears 
gray, and for this reason this disease has been called ''Brown Rot" 
and "Gray Rot." 
This disease is likely to make its appearance in this State about 
the first of July. It requires for its rapid and complete develop 
ment a wet and warm atmosphere. A dry spell of weather will 
greatly check its growth. 
Remedy. — The treatment prescribed for the black rot will serve 
to control the downy mildew. Since the fungus of this mildew 
grows within the tissue of the leaf, it is apparent that it entered 
sometime previous to the appearance of white patches. Conse- 
quently, since fungicides are preventives and not destructives, the 
Bordeaux mixture should be applied as early as the first of June. 
Four sprayings, applied at intervals of two weeks, will serve to keep 
the vines in good health and permit the normal development of the 
crop of fruit. 
POWDERY MILDEW. 
( TJncinula spiralis.) 
This fungus is like the preceeding one, a native of America, and 
like it attacks the wild and cultivated grape. The European varie- 
ties are particularly subject to the attack of the Powdery Mildew. 
The Downy and Powdery Mildews are often found in the same vine- 
yard, but there are points of difference by which they can readily be 
distinguished. The former thrives in wet weather, the latter in dry 
weather. The former fruits on the under side of the leaf, the latter 
upon the upper side. The mycelium of the Downy Mildew is wholly 
internal to the plant, while that of the Powdery Mildew is wholly ex- 
ternal to the plant, spreading over the upper surface of the leaf. 
