﻿COPPER SPRAYS ON IRISH POTATO TUBERS. 



13 



Connecticut were well infected with late blight before any Bordeaux 

 spray was applied. All the plants died early; consequently, it is not 

 surprising that the tubers showed no effect of the Bordeaux spray, 

 probably because they were formed before the first spray was applied 

 and were therefore too far advanced to derive any benefit from the 

 sprays. The New Jersey results for solids were not higher for the 

 tubers from the copper-sprayed than for those from the unsprayed 

 plants in the case of all samples examined, although the average 

 figures were higher for the tubers from the Bordeaux-sprayed plants. 

 A discussion of the use of Bordeaux spray on potatoes in New Jersey 

 by Lint (SO) is interesting in this connection. He considers the cli- 

 mate, cultivation, and fertility of the field to be important factors in 

 determining to what extent Bordeaux is beneficial to the potato. Ac- 

 cording to this author, Bordeaux prolongs the life of the vines and 

 affords the best control of flea beetle, although increased yield of 

 tubers does not consistently result from the application of Bordeaux 

 to potato plants in New Jersey. 



It has been the writer's experience that an occasional sample of 

 tubers from a check plot will run higher in solids, starch, and nitrogen 

 than a sample from a Bordeaux- or other copper-sprayed plot. This 

 is the exception to the rule, however, and may be due to the inclusion 

 among the tubers selected for analysis of a potato or several potatoes 

 that are not hard and firm. Sometimes one of the tubers in a hill is 

 a little softer than the rest, probably because the food supply has 

 been limited or checked in some way. In work of this kind average 

 figures are undoubtedly the only criterion. 



1920 DATA. . 



Arlington Experimental Farm, Va. — In the spring of 1920 experi- 

 ments were carried out at Arlington Experimental Farm, using Irish 

 Cobbler, Early Ohio, and Early Rose varieties of potatoes. Spald- 

 ing Rose, Gold Coin, Irish Cobbler, and McCormick potatoes were 

 grown in the fall. A 4-4—50 Bordeaux spray, a Pickering spray, a 

 10-10-50 Bordeaux, and a 0-4-50 spray were used. The check plots 

 and all the copper-sprayed plots received a lead arsenate spray. The 

 figures reported in Table 4 are the averages for 53 sets of tubers 

 separately analyzed. 



Table 4. — Yield and composition of tubers from sprayed and unsprayed potato 

 plants, Arlington Experimental Farm, Va., August and October, 1920. 



Variety. 



Treatment. 



Yield 



from 



2 rows, 



each 100 



feet long. 



Composition of tubers. 



Solids. Starch. Nitrogen 



Earlypotatoes (August): 

 Irish Cobbler x 



D02 



Do 1 



Do i 



Doi 



Early Ohio 1 



Do 1 



Do 



Early Rose 1 



Do 1 



Do 1 



4-4-50 Bordeaux 



Cheek (no copper) 



Pickering spray 



10-10-50 Bordeaux 



0-4-50 spray (no copper) . 



4-4-50 Bordeaux 



Check (no copper): 



Pickering spray 



4-4-50 Bordeaux 



Check (no copper) 



Pickering spray 



Pounds. 

 357 

 321 

 340 

 341 

 350 

 217 

 216 

 211 

 245 

 228 

 229 



Per cent. 

 19.91 

 19.59 

 20.64 

 20.42 

 19.85 

 19.17 

 19.28 

 19.44 

 20.18 

 18.97 

 20. S6 



Per cent. 

 14.20 

 13.70 

 14.50 

 14.70 

 13.90 

 13.90 

 13.90 

 14.70 

 14.38 

 13.60 

 14.83 



Per cent. 

 0.372 

 .368 

 .383 

 .367 

 .356 

 .412 

 .410 

 .433 

 .367 

 .326 

 .364 



1 Average of 2 sets. 



2 Average of 4 sets. 



