EXPERIMENT STATION BULLETINS. 267 



Cost of spraying 27 acres : 



450 lbs. Copper Sulphate |30 50 



2 bbls. Lime 2 00 



Man 9 days (also board) 18 00 



Horse 9 days 9 00 



20 per cent interest on sprayer 10 00 



Total 169 50 



Average cost per acre for single spraying about 45c to 50c. Our 9-acre 

 field, planted May 20, was sprayed six times in the rainy season and 

 the mixture was washed off every other day, no chance, in fact this field 

 died early, September 20. The yield was 140 bushels." 



The above statement of Mr. Swan goes to show that spraying for late 

 blight is a sound business proposition. * 



IV. RESULTS OBTAINED IN OTHER STATES. 



One of the first field experiments in spraying potatoes for late blight 

 was made by Jones of the Vermont Experiment Station in 1889. Spray- 

 ing experiments for blight at that Station have been kept up for a 

 great many years and the results have always been the same; i. e., that 

 it pays. Some of the results obtained in Vermont, picked at random 

 from a long term of years, will be of interest to Michigan growers. 

 Results obtained in 1892.* 



Plots sprayed with Bordeaux mixture gave 324 bushels per acre. 



Adjoining plots unsprayed gave 100 bushels per acre. 



Gain from the use of Bordeaux mixture, 224 bushels per acre. 



Results of 1893, a bad blight year: 



Plots sprayed with Bordeaux mixture yielded 375 bushels per acre. 



Adjoining plots unsprayed yielded 121 bushels per acre. 



These gains by spraying are probably a great deal larger than 

 could be obtained in large fiel/i experiments in Michigan. 



In 1900 the Maine Stationf experimented in spraying for blight in 

 a small way and the increase in yield per acre for potatoes sprayed 

 with Bordeaux mixture was 133 bushels per acre over those not sprayed. 



Perhaps, however, the most extensive and the most carefully con- 

 ducted experiments in potato spraying have been carried on at the 

 New York Experiment Station, Geneva, N. Y. The results of their 

 first year's experiments, 1902,1 gave a yield of 317^2 bushels per acre 

 for rows sprayed three times; 3421/^ bushels per acre for rows sprayed 

 seven times, and 219 bushels per acre for those not sprayed at all. Thus 

 the seven sprayings gave an increased yield of 1231/2 bushels per acre 

 and the three sprayings 98i/^ bushels per acre. 



The following year, 1903,1| the Geneva Station enlarged its field of 

 work along this line and established a number of cooperative business 

 experiments with farmers throughout the state. 



"The farmers business experiments were designed to determine the 



* Vt. Bulletin No. 72, p. 15. 

 Bulletin 73 Maine, p. 57 



N. Y. Expt. Sta. Bulletin No. 221, pp. 235-6. 

 For complete account see N. Y. Expt. Sta. Bull. No. 241. 



