122 



Annals of Horticulture. 



adopted this formula, but I used only 3.3 pounds of the sul- 

 phate. Three varieties of potatoes were used, and each va- 

 riety was grown on four plats, three of which were treated 

 with the Bordeaux mixture made with 6.6, 3.3, and 2.2 

 pounds of copper sulphate, lime 3.3 pounds, water 26 gallons. 

 The best results were obtained from the plats treated with 

 the mixture which contained 3.3 pounds of the sulphate, and 

 I believe that equally good results may be obtained with 2.2 

 pounds if the applications are made early enough and re- 

 peated every two or three weeks. Whatever the amount of 

 the sulphate used, if the lime is good only one-third as much 

 by weight need be used as is taken of the sulphate. An ex- 

 cess of the lime makes the mixture less adhesive. 



" The Early Violet potato is so susceptible to the disease 

 that formerly I lost all my plants at least once each year for 

 three years in succession. This year, in spite of the contin- 

 uous rains, I did not find one diseased potato when they were 

 dug, which was on the 1st of August. Another examination 

 otato- was ma( ie i n November, and only nine diseased potatoes were 

 rot in found, and these were only slightly injured. This was only two 

 lrope * per cent, of the total yield. The same is also true of Royal 

 Ash-Leaved and Wonderful or Kidney. A treated plat of 

 White Schelderode yielded 29,413 kilograms, while an un- 

 treated plat of the same size, and adjoining the first, yielded 

 only 17,842 kilograms. The number of diseased tubers on 

 the first plat was 180 kilograms against 7,646 in the untreated 

 plat. These figures should convince every one of the value of 

 spraying to prevent the rot of potatoes. But more, by finding 

 the average gain per hectare of the 71 experiments, we find 

 that it is 4,970 kilograms, or 73.7 bushels per acre. In calcu- 

 lating this average, the total failures are included as well as a 

 large number of highly susceptible varieties. 



"In Belgium the disease usually makes its appearance early 

 in July. Since it requires some days for the disease to pro- 

 gress far enough to become visible, it is evident that applica- 

 tions should be made earlier, from the 15th to the 25th of 

 June. For very early varieties which are planted late in 

 March, the operation may be performed from 10 to 15 days 

 earlier. The second application should be made in about 18 

 days, and during rainy weather it should not be delayed more 

 than two weeks. Ordinarily two applications are sufficient both 



