﻿2 BULLETIN 1146, U. S. DEPARTMENT OF AGRICULTURE. 



When in 1917 it was found that the solids, starch, and nitrogen 

 contents of tubers from copper-sprayed potato plants were greater 

 than those of tubers from unsprayed plants, an investigation was 

 begun in the Bureau of Chemistry to determine the effect of Picker- 

 ing sprays, barium-water sprays, and standard Bordeaux sprays as 

 compared with that of noncopper sprays on the yield and on the com- 

 position of potatoes grown in different localities. The distribution 

 of copper in the tubers, roots, stems, and leaves of the various 

 sprayed and unsprayed potato plants was studied also. 



RESULTS OF PREVIOUS INVESTIGATIONS. 



YIELD OF POTATOES. 



Giddings (SO) ,* of the West Virginia station, fund that in 1909 

 three applications of Bordeaux increased the yield of potatoes 53.5 

 per cent and that in 1910 four applications increased the yield 39.3 

 per cent. 



In New York Stewart and his associates (46 \lft \4$) have conducted 

 an extensive series of experiments to show the benefits of Bordeaux 

 spraying. In discussing the results obtained at the New York station 

 in 1911 Stewart stated : " There was no late blight whatever, onty a 

 very little early blight and very little flea-beetle injury. The un- 

 sprayed rows were affected bj^ no disease of any consequence except 

 tip burn and even of that there was only a moderate amount, * * * 

 yet spraying increased the yield at the rate of 93 bushels per acre. 

 Plainly we have here a striking example of the beneficial influence of 

 Bordeaux in the absence of disease and insect enemies." 



In 1912 Lutman (32) published data from Vermont showing that 

 a greater yield of tubers was obtained from copper-sprayed potato 

 plants at various stages of growth than from the unsprayed plants. 

 Plants which receh T ed a Pickering spray, a Bordeaux spray in which 

 part of the copper sulphate had been replaced by iron sulphate, and 

 a commercial spray containing copper also gave higher yields than 

 the check plants. The increased yield seemed to be in proportion to 

 the amount of copper present in the spray. The application of a 

 spray containing silver did not increase the yield. Lutman sug- 

 gested that the Bordeaux mixture acts as a stimulant, bringing about 

 an increase in the quantity of starch produced daily. 



Clinton (8) in 1915 reported that homemade Bordeaux sprays used 

 on potatoes in Connecticut uniformly increased the yields. The 

 average increase for the sprayed plants during the 13 years that the 

 tests were carried on was 36 bushels an acre. 



In 1916 Lutman (33) reported the results he obtained in 1912 from 

 using 5-5-50 Bordeaux and 2£-2£-50 Bordeaux on potatoes in Ver- 

 mont. He concluded that " the amount of copper sulphate and lime 

 used did not appear to be important providing the mixture was fairly 

 strong. A little difference appeared in favor of the 5-5-50 combina- 

 tion over the 24-2|— 50. Frequent and early sprayings did not seem 

 favorably to affect the yield of tubers. Some of the plants were 

 sprayed ten times but they produced little or no larger crops than 

 did those plants sprayed less often." He stated further that the use 



1 Italic figures in parentheses refer to literature cited at end of bulletin. 



