﻿UNITED STATES DEPARTMENT OF AGRICULTURE 



Mlf BULLETIN No. 1146 j^ 



3SH 



^..Tt. 



WASHINGTON, D. C. PROFESSIONAL PAPER 



April 5, 1923 



THE INFLUENCE OF COPPER SPRAYS ON THE 

 YIELD AND COMPOSITION OF IRISH POTATO 

 TUBERS. 



By F. C. Cook, Physiological Chemist, Insecticide and Fungicide Laboratory, 

 Miscellaneous Division, Bureau of Chemistry. 



CONTENTS. 



Page. 



Purpose of investigation 1 



Results of previous investigations : 



Yield of potatoes 2 



Composition of potatoes 3 



Plants in general 4 



Experimental procedure 7 



Results of experimental work : 



Changes in composition of tubers 



during growth 7 



Effect of copper sprays on yield 



and composition of tubers 10 



Proportion of tubers to' vines 



plus tubers 16 



Page. 

 Results of experimental, work — Con. 

 Influence of strength and num- 

 ber of applications of copper 

 sprays on composition of 



tubers 17 



Influence of environment on com- 

 position of tubers 18 



Copper content, of vines, stems* 

 roots, and tubers of sprayed 



and unsprayed plants 19 



General discussion 21 



Summary 23 



Literature cited 24 



PURPOSE OF INVESTIGATION. 



For years Bordeaux sprays have been applied to the potato plant 

 to control fungous diseases, particularly in the northern parts of the 

 country where the late blight (Phytophthora infestans) frequently 

 causes serious losses. In those parts of the Central and Southern 

 States where potatoes are grown the only spray ordinarily applied 

 is .an arsenical to control the Colorado potato beetle. Arsenicals are 

 usually added to the Bordeaux sprays. The formulae of Bordeaux 

 sprays may vary in different localities. A 5-5-50 spray is one in 

 which 5 pounds of copper sulphate and 5 pounds of lime are used 

 and the spray is made to 50 gallons with water. 



The fact that potato plants treated with Bordeaux spray give 

 larger yields of tubers than those which do not receive such applica- 

 tions has been established by a series of experiments extending over 

 many years at the Vermont, Maine, and New York agricultural ex- 

 periment stations. The influence of the copper sprays on the com- 

 position of the tubers, however, has received no detailed study in this 

 country. In view of the importance of the potato crop it is surpris- 

 ing that practically no detailed analyses of potato tubers grown in 

 the United States are available. 



27475°— 23 1 



