248 MANUAL OF FRUIT DISEASES 



(1) when the shoots are about six or eight inches long; (2) 

 during or just before blossoming; (3) later applications are 

 necessary only on very susceptible varieties or where irrigation 

 is practiced when grapes are half -grown. Winter treatments 

 are not generally commendable. The cost, including material 

 and labor, varies from forty to fifty cents the acre for one treat- 

 ment. Where it is necessary to treat vines for downy-mildew 

 and black-rot, bordeaux mixture may be suitable for powdery- 

 mildew. Liquid fungicides, however, are not as effective as 

 sulfur dust, and in vineyards where this disease is particularly 

 troublesome along with other diseases, it is best to follow the 

 bordeaux sprayings with dust. 



The fungus shows preference for European vines ; all Amer- 

 ican varieties are less susceptible. These points are worth 

 remembering in planting the vineyard where powdery-mildew 

 is prevalent. 



REFERENCES 



Bioletti, F. T. Oidium or powdery mildew of the vine. California 



Agr. Exp. Sta. Bui. 186 : 315-350. 1907. 

 Reddick, D., and Gladwin, F. E. Powdery mildew of grapes and its 



control in the United States. Int. Cong. Vit. Rept. 1915: 117- 



125. 1915. 

 Bioletti, F. T., and Flossfeder, F. C. H. Oidium or powdery mildew 



of the vine. California Agr. Exp. Sta. Circ. 144 : 1-12. 1915. 

 Scribner, F. L. Report on the fungus diseases of the grape vine. 



II. The powdery mildew. U. S. Agr. Dept. Bot. Div. Plant 



Path. Sec. Bui. 2 : 18-28. 1886. 

 Jackson, H. S. Grape diseases. Powdery mildew. Oregon Crop Pest 



and Hort. Bienn. rept. 1911-1912 : 269-270. 1913. 

 Scribner, F. L. The powdery mildew. U. S. Agr. Comm. Rept. 1886 : 



105-109. 1887. 

 Scribner, F. L. Distribution and severity of the grape mildews and 



black rot in the United States. U. S. Agr. Comm. Rept. 1886 : 115- 



116. 1887. 



