12 



UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



The sprays used,* the dates of their application, the amount of each 

 used per acre, and the length of the vine shoots when they were applied, 

 are given in the following tables. From these tables the cost of the 

 spraying, exclusive of the labor, may be approximately determined: 



Amount of spray used on fair vines of the Burger variety; 1210 vines per acre. 



On the South Sonoma experiment plot half of the intended spraying 

 with the iron sulfate was carried out. 



Amount of spray used on old, large vines of the Mission variety; 680 vines per acre. 



The growth of the vines at the East Sonoma experiment plot was too 

 uneven to be of value for tabulation. 



The three experiment plots very soon proved to be of very unequal 

 value for the study of the Red-leaf disease. The vines in the East 

 Sonoma plot were practically not affected by this disease, though seri- 

 ously menaced by one which will be described below under the name of 

 Grape-shrivel. The Red-leaf disease was prevalent in the North Sonoma 

 plot, but so also was the Root-rot. At the South Sonoma plot, however, 

 the vines were not affected with any other disease than the Red-leaf, 

 and it is there that practically all the data on the development and 

 progress of this malady were gathered. Notwithstanding the presence 



*The sprays used were: 1.25 per cent Bordeaux mixture, and acid iron sulfate. The 

 acid iron sulfate is prepared as follows: Ten pounds of iron sulfate are placed in a half- 

 barrel, one pound of commercial sulfuric acid is poured into the copperas (to prevent 

 sputtering, which is objectionable, the acid should always be added before the water), 

 then 12.5 gallons of water are added and the mass stirred until the sulfate has dissolved. 

 In making large quantities of the acid iron sulfate spray it is more expeditious to use 

 hot water. The iron sulfate is only a winter spray, and can not be used after the buds 

 have swollen. 



