POTATO DISEASES "*IN I907. 295 



DISCUSSION OF RESULTS. 



So far as the results of the foregoing experiments show, none 

 of the substitutes for wet bordeaux in any way approached it 

 in efficiency as a preventive for late blight. While none of the 

 dust sprays in any way produced the results claimed for them 

 by the manufacturers and others, they all showed more or less 

 fungicidal value. This was least with Leggett's Blight Dust 

 No. 2 and Bowker's Dry Boxal, which only showed a gain of 

 18 or 20 bushels per acre resulting from 6 applications of 6 

 pounds each, when compared with the unsprayed check. The 

 same amount of Dust Sprayer Manufacturing Co's. Sal Bor- 

 deaux increased the yield 60 bushels per acre, while 10 pounds 

 of the same material to an application gave an increase of 102 

 bushels per acre. The fact should not be overlooked that wet 

 bordeaux under the same conditions gave an increase of 168 

 bushels per acre. The value of the wet bordeaux as compared 

 with the dust sprays is more apparent from the last column of 

 the table. Estimating the value of potatoes at 50 cents per 

 bushel, which was about the price being paid when the crop 

 was dug, it will be seen that the loss from dusting as compared 

 with the average yield of the wet sprayed plots varied from 

 $33.00 per acre from using 10 pounds to an application of Sal 

 Bordeaux to $75.00 per acre where 6 pounds of Leggett's Blight 

 Dust No. 2 was used per application. Sodium Benzoate Bor- 

 deaux and Bowker's Boxal Paste, the former containing only 

 one pound of copper sulphate and one-half pound of sodium 

 benzoate to 50 gallons of spray, gave better results than each 

 of the dust sprays except the 10-pound application of Sal Bor- 

 deaux. However, there does not appear to be any particular 

 merit in them as substitutes for standard bordeaux. Boxal 

 paste costs in 100-pound lots about 3 times as much as the 

 materials to prepare an equal amount of home-made bordeaux, 

 and the writer found it nearly as much work to get the paste 

 in proper condition for spraying as it was to make the same 

 quantity of bordeaux. Unfortunately no check plot treated 

 with a bordeaux mixture containing one pound of copper sul- 

 phate to 50 gallons of water was provided, so it is impossible 

 to say whether the partial protection on Plot 7 was due entirely 

 to the small amount of copper sulphate which it contained or in 



