Diseases of the Potato. . 317 



Mr. McNair grew a number of acres of White Star potatoes, and 

 in his field the plots and sections were laid out so that four rows 

 extended from one end of the plantation to the other. Only tlie 

 two central rows were considered when the yields were measured. 

 The potatoes were planted May 28, and were sprayed with the 

 Bordeaux mixture July 19 and August 5. This mixture was made 

 of different strengths. 



a. The most concentrated form contained 6 pounds copper sul- 

 phate, 4 pounds quicklime, and 40 gallons of water. 



h. This mixture contained 5 pounds copper sulphate, with lime 

 in the above proportions, in 40 gallons of water. 



c. The amount of copper sulphate was reduced to 4.3 pounds in 

 40 gallons, with lime in proportion. 



d. Only 3 . 5 pounds copper sulphate were used to 40 gallons, the 

 amount of lime being likewise reduced. 



Five sections were selected, each having four rows and containing 

 24 square rods. One section remained untreated, but the remainder 

 were sprayed with the different mixtures. This was done by an 

 efficient power sprayer which Mr. McNair had made. Yermorel 

 nozzles w^ere used, and very satisfactory work was done, although 

 the amount of liquid applied might perhaps have been increased to 

 advantage. 



When the potatoes were dug in the fall the following yields were 



obtained, the figures again showing the proportionate amounts per 



acre : 



Section 1, Untreated, 209 bushels. 



" 2, Mixture a, 227 " 



3, '' I, 234 '' 



u 4^ u ^^ 221 '' 



" 5, " d, 191 " 



These figures are not altogether encouraging for the sprayer. 

 Sections 2, 3 and 4 on the average yielded an increase of only 18.3 

 bushels per acre, while section 5 produced 18 bushels less than the 

 untreated one. These figures appear to represent the actual gains, 

 yet no apparent reason exists for the decreased yield of section 5. 

 Probablv local conditions of the soil exerted this influence. 



I^lot 1 V. This plot was situated in another part of the field. 

 Only two sections were made, these being still larger than in the 

 preceding experiment. The most concentrated Bordeaux mixture 

 above mentioned was applied to one, the other remaining untreated. 



