﻿COPPER SPRAYS ON IRISH POTATO TUBERS. 3 



of Bordeaux under field conditions increases the yield of tubers from 

 potato plants by preventing tip burn and fiea-beetle injury. lie be- 

 lieved that the yields are not increased when plants which arc no! 

 troubled by tip burn or flea beetle are sprayed. According to this 

 investigator, Bordeaux mixture seems in the long run to be neither 

 beneficial nor harmful, but it is unnecessary to apply it to plants 

 grown in the greenhouse or to those in regions where neither tip 

 burn nor flea beetles are a factor in potato growing and where neither 

 early nor late blight occurs. 



Babcock (4) reported in 1917 that spraying potatoes thoroughly 

 with a 4 1 50 Bordeaux mixture in Ohio when the plants were about 

 8 inches high and every 10 days to two weeks thereafter materially 

 increased the yield, even in years when there were no disease epi- 

 demics. 



Erwin (16) reported a difference in yield in favor of the Bor- 

 deaux-sprayed plots, indicating a definite response to the use of 

 Bordeaux spray in Iowa. When tip burn was generally present and 

 early blight practically absent the yields were higher on the sprayed 

 plots, indicating that the plants had been stimulated and benefited 

 by the Bordeaux application. 



In 1919 Leiby (29) published data obtained in North Carolina 

 showing an average gain of 51.6 bushels an acre, representing 64.2 

 per cent, as a result of the use of a 3^^50 Bordeaux plus lead 

 arsenate spray on potatoes. Bordeaux alone produced an increased 

 yield of 35 bushels an acre. 



During a 10-year period in New York an average gain of 60 

 bushels an acre was obtained by spraying with Bordeaux. At the 

 Vermont station during 20 years, which covered all seasonal varia- 

 tions, an average gain of 105 bushels of potatoes an acre was effected 

 by the use of Bordeaux. Experiments at the Maine station extend- 

 ing over a period of years showed that spraying with Bordeaux gave 

 increased yields of tubers, even in years when no late blight was 

 prevalent. 



COMPOSITION OF POTATOES. 



Although no detailed analyses of potatoes grown in the United 

 States are available, the results of several analytical studies of 

 European varieties have been reported. 



Kreusler (26) gives the results of analyses of large, medium, and 

 small tubers grown in Germany. They had the same general com- 

 position, the only difference being the presence of slightly more crude 

 fiber and solids in the small than in the large tubers. The medium- 

 sized tubers had more crude fiber than the large tubers but the same 

 proportion of solids. 



Appleman (2), who investigated the changes in Irish potatoes 

 during storage, gives data on the moisture, total sugar, and starch 

 contents. 



Girard (21) in 1889 reported the changes taking place in tubers in 

 France during growth. The sucrose content dropped from 1.48 to 

 0.02 per cent and the dextrose content from 0.67 per cent to none. 

 Protein increased from 1.36 to 1.98 per cent, ash from 0.86 to 1.46 

 per cent, starch from 8.4 to 16.38 per cent, and cellulose from 0.84 

 to 1.66 per cent. The insoluble nitrogen dropped from 1.66 to 0.19 

 per cent and the insoluble ash from 0.16 to 0.06 per cent. 



