PLANT-DISEASES. 61 



Downy Mildeav, Brown-Rot, Gray-Rot (Peronospora 

 viticola, De Bary). — Appears in small frost-like patches 

 on the under surface of the leaves, and causes yellowish 

 discoloration on the upper surface. It also produces the 

 brown-rot and the gray-rot of the fruit. The young ber- 

 ries remain small and firm, usually not wrinkled, being at 

 first gray in color, while the older ones become brown. 

 The disease is worst on thin and smooth-leaved varieties, 

 as the Delaware and others. It extends generally through- 

 out N. America. Of American origin. 



Preventive. — A wide board nailed flatwise on the top of 

 the trellis so as to protect the vines somewhat, as with 

 a roof, is a considerable protection, as it tends to keep 

 the vines dry. Vines trained against a building rarely 

 suffer. 



Bemedies. — The same as for black-rot, which see. 



Powdery Mildew {Uncinula spiralis^ B. &, C). — Appears 

 early in the season as delicate dust-like patches or covering 

 on the leaves, mostly on the upper surface, and on shoots 

 and fruits. Berries attacked by it become checked in 

 growth, and may remain small and die, or they sometimes 

 grow and crack before death ensues. It attacks grapes in 

 vineries whfch are not properly ventilated and managed. 

 Occurs generally throughout the Union, but is less destruc- 

 tive than the downy mildew. American origin. 



Bemedies. — Dry sulphur applied to the vines, two or three 

 times — once when the shoots just begin to push, again 

 when in blossom, and usually again shortly before the 

 grapes begin to turn. Apply in warm and bright weather, 

 after the dew is off. In vineries, the sulphur may be scat- 

 tered on the hot pipes. Any of the sprays of copper com- 

 pounds are specifics, and are to be recommended for use in 

 vineyards suffering from the disease, in preference to sul- 

 phur. 



Rattles. — A shelling of the grapes from the cluster when 

 they are nearly ripe. Particularly serious in western New 

 York. It is supposed to be due largely to lack of available 



