1318 



THE FRUIT INDUSTRY IN NEW YORK STATE 



damage is on foliage, and the presence of -the disease on leaves 

 may be confirmed with certainty by inverting brown-spotted leaves 

 and examining for a white, frost-like growth. Eventually the old 

 spots spread or new spots develop and the leaf turns brown and 

 dies, thus leaving the fruit sour and unripe. 



The disease may be controlled by spraying as for black rot. 

 Ordinarily the two early applications are sufficient to hold the 

 disease in check, but in the case of early autumn rains the later 

 application may prove of great benefit. 



POWDERY MILDEW 



This disease is common 

 wherever grapes are grown, 

 but is most destructive in the 

 Chautauqua belt. The Rogers 

 hybrids are especially sus- 

 ceptible to it, but the disease 

 is of greatest importance be- 

 cause of its prevalence on 

 the Concord. The disease is 

 caused by a superficial 

 fungous parasite r Uncinula 

 necator. The fungus passes 

 the winter on affected fallen 

 leaves and perhaps also on 

 the canes. It rarely becomes 

 active until the middle of 

 July or later, and often the 

 first spots of the disease are 

 not found until the middle 

 of August. Small, grayish- 

 white spots appear on all 

 green spots of the vine. They 

 are noticable first on the foli- 

 age. They increase in size 



FIG. 456. POWDERY MILDKW ON 



GRAPES 



The fungus spreads over the berries 

 and prevents their normal develop- 

 ment. The lower berry is nearly 

 normal. The pedicles and peduncles 

 are also affected and shrivel very 

 quickly after harvest. 



and eventually cover the entire leaf. The presence of the fungus 

 on the peduncle of the cluster is most serious, since it weakens the 

 stem, which shrivels very rapidly when the cluster is removed 

 from the vine. 



