DISEASES OF CROPS 213 



buds open and then at intervals of three weeks until the fruit is two- 

 thirds grown. 



NOTE. There are several other leaf diseases of the gooseberry and 

 currant that may occasionally prove injurious or destructive and should 

 be treated as the circumstances may demand. 



GRAPE 



Black Rot (Guignardia bidwellii [Ell.], V. and R.). This very common 

 disease of the grape attacks the fruit, causing a black rot followed by a 

 shriveling and drying into a hard, wrinkled mummy. It occurs on the 

 leaves and young shoots earlier than on the fruit and causes tan-colored 

 spots with minute black dots in the centers. 



Treatment. Spray with Bordeaux mixture before the opening of 

 the flower-buds, and again after the setting of the fruit. Addi- 

 tional spraying should depend on the weather; in dry seasons it may 

 be necessary to spray every three weeks until the fruit is two-thircls 

 grown. 



Bird's Eye or Anthracnose (Sphaceloma ampelinum, DeBy.). This 

 disease is not nearly so severe as the black rot. It attacks the fruit, causing 

 brown or black spots with sunken centers and red borders. On the canes 

 it causes similar spots, but as they approach maturity the centers beconie 

 ashy hi color and the edge dark. 



Treatment. Badly diseased canes should be cut out and burned. 

 Spray treatment same as for black rot. 



Bitter Rot or Ripe Rot. This is the same as on the apple but its attack 

 is confined to the ripe fruit. 



Treatment. Spray with ammoniacal copper carbonate solution. 



Downy Mildew (Plasmopara viticola [Berk, and Curt.], Berl. and De 

 Toni.). This fungus causes whitish and finally brownish areas in the leaf, 

 followed by a very perceptible downy growth on the lower surface. It 

 sometimes causes the death of the entire leaf, shoot or vine. It is especially 

 severe on the European varieties. It sometimes attacks the fruit, causing 

 the gray or brown rot. 



Treatment. Same as for black rot. 



Powdery Mildew (Uncinula necator [Schw.], Burr.). This fungus is 

 very similar to the powdery mildew of the apples and other fruits. It 

 attacks all parts of the plant above ground, and occurs on both upper and 

 lower surfaces of the leaves, causing circular, whitish, powdery spots which 

 frequently unite and cover the entire leaf. It also attacks the fruit, causing 

 it to develop irregularly, fail to develop or to fall. It is especially common 

 in vineyards where the vines are too closely set and on vines grown under 

 glass. 



Treatment. Spray with potassium sulphide or when the temperature 

 is above 75 F., sprinkle the vines with flowers of sulphur. 



Necrosis (Fusiwccum viticolum, Reddick). This disease causes a 



