832 Popular Editions of Station Bulletins of the 



were carefully kept so that the exact financial gain or loss from 

 spraying could be obtained. From six to fifteen potato growers 

 co-operated with the Station in this work each year, the fields 

 imder test including from 60 to 225 acres annually. In all, there 

 were 114 different trials and in only 20 cases did spraying fail to 

 give a profit. That is 17^2 per ct. of the acreage sprayed caused 

 the owners a loss of $1,286.74; while the other fields gave a net 

 profit, after all expenses had been met, of $20,786.75. Taking 

 the experiments as a whole, failures and successes together, spray- 

 ing resulted in an average gain of 36.1 bu. to the acre and an 

 average net profit of $14.43 an acre. 



Volunteer experimenters reporting to the Station give an even 

 better showing, as the 205 experiments made by them in seven 

 years give an average gain of 54.3 bu. to the acre. These last 

 results are, of course, better than the average gains by farmers 

 in the years reported, since growers are less apt to announce fail- 

 ures than successes; but in the farmers' business experiments 

 failures and successes were all recorded alike. Even these results 

 could be much bettered by more thorough work, as is shown by 

 the acreage increases in yield shown by the Station tests. In these 

 Station experiments, the bordeaux was applied very thoroughly, 

 with a knapsack sprayer; so that efficient protection was given 

 the plants. Such protection is not ordinarily secured by machine 

 spraying by farmers ; but care in application and " double spray- 

 ing " have usually given profitable increases. 



During the last two years of the tests ar- 

 "^ ^,^ rangements were made with several growers 



. to " double spray " portions of their fields ; 



that is, to go both up and down the same rows 

 with the sprayer. Both of these years were very dry and spray- 

 ing, therefore, of less benefit than usual. While there were some 

 very surprising exceptions to the rule, the double spraying was 

 profitable, as shown by the following table : 



