242 MANUAL OF FRUIT DISEASES 



of short duration followed by sunshine and winds are not 

 favorable to the spread of the fungus. Most injury is done 

 during hot, wet weather. 



Control. 



Since the fungus hibernates in old fallen leaves it is commonly 

 recommended that these be plowed under early in the spring. 

 The real value of such an operation, however, is not definitely 

 known. The vines should be sprayed to protect them against 

 attacks of the downy-mildew pathogene in any case. Use 

 bordeaux mixture 5-5-50, making five or six applications 

 during the season. The first should be made just before the 

 blossom buds open ; the others at intervals of two weeks. 



REFERENCES 



Istvanffi, G. Etudes sur le rot livide de la vigne. Hongrois Royal 



Inst. Cent. Ampel. Ann. 4 : 1-260. 1913. 

 Viala, P. Les maladies de la vigne, pp. 57-185. 1893. 

 Farlow, W. G. On the American grape-vine mildew. Bussey Inst. 



Bui. 1 : 415-425. 1876. 

 Gregory, C. T. Spore germination and infection with Plasmopara 



viticola. Phytopath. 2 : 235-249. 1912. 

 Shear, C. L. Insect and fungous enemies of the grape east of the 



Rocky Mountains. U. S. Agr. Dept. Farmers' Bui. 284 : 30-32. 



1907. 

 Gregory, C. T. Studies on Plasmopara viticola (Downy mildew of 



grapes). Int. Cong. Vit. Rept. 1915 : 12&-150. 1915. 



POWDERY-MILDEW 



Caused by Uncinula necator (Schw.) Burr. 



The powdery-mildew, or oidium, of the vine is native to the 

 Old World, originating on native plants in Japan. It was at 

 one time erroneously held that this disease, like black-rot and 

 downy-mildew, originated on wild vines of the eastern and 

 central United States. The disease first appeared in Europe 



