9 



for comparison. The spraying was repeated July 26, August 

 8, 21, and September 4. 



The early blight did not make its appearance in the field until 

 about the time of the third spraying, August 8, and did not 

 begin to seriously affect the unsprayed vines until two weeks 

 later. By the middle of September, however, the unspraj'ed 

 vines were dead, while the sprayed vines, in varying proportions 

 in dift'erent parts of the field, were alive the first of October 

 when the potatoes w^ere dug. 



Owing to the uneven character of the field and the effects of 

 the drouth, the yield of the sprayed plots as a whole could not 

 be compared with that of the unsprayed plots. Smaller plots 

 of each, as similar in character as possible, were chosen and 

 and the yields compared. Five pairs of plots were selected, 

 each consisting of a sprayed and an unsprayed plot of equal 

 size lying side by side. The sprayed plots showed an increase 

 in yield over the unsprayed as follows : 



Pair No. 1 an increase of '2H.1 bushels per acre. 



The average increase per acre apparently due to spraying was 

 33 bushels. 



The cost per acre of each spraying was $3.52; for the five 

 sprayings, S17.60. The potatoes were sold for 60 cents per 

 bushel. At this price the 33 bushels were worth $19.80. De- 

 ducting the cost of spraying, $17.60, there was left a profit of 

 $2.20. This, as it stands, would not be a ver}^ brilliant result, 

 but there are several circumstances which should be taken into 

 consideration along with it. It seems probable that three 

 sprayings, beginning the first of August, would have answered 

 as well as the five, beginning the seventh of July. Sprajnng was 

 begun at this early date to make sure of getting ahead of the 

 blight, which, however, did not appear till about the middle of 

 August. Had three sprayings only been made, the cost would 

 have been $10.56 and the profit $9.24 per acre. It is probable 

 that owing to the drouth and the late appearance of the blight, 



