SPEAYING POTATOES 



NOW IS THE TIME TO PREVENT BLIGHT AND ROT; 



W. T. MACOUN, C. E. F., OTTAWA. 



NOTWITHSTANDING the fact 

 that year after year the potato 

 crop in Canada is very much less- 

 ened by blight and rot, and that this blight 

 can be prevented to a large extent by spray- 

 ing, comparatively few farmers spray their 

 potatoes to prevent this disease. It has 

 been known for about eighteen years that 

 Bordeaux mixture will prevent the blight, 

 and it has been frequently demonstrated by 

 experimenters and by other growers of po- 

 tatoes that the crop is much increased by 

 spraying. In order, however, to get potato 

 groAvers to spray it is necessary to keep con- 

 stantly demonstrating the value of it. The 

 results of the tests made at the Central Ex- 

 perimental Farm, Ottawa, in 1902 and 1903 

 should be sufficient to induce everyone who 

 lives in a disease-infected district to spray. 



In 1901 eight varieties were tested. The 

 average increase in yield per acre of the 

 eight varieties, where sprayed, was 94 bush- 

 els. In one variety, however, there was an 

 increase of 171 bushels, and in another 155 

 bushels per acre. 



In 1902 eleven varieties were tested. The 

 average increase in yield of marketable po- 

 tatoes, where sprayed, was 120 bushels per 

 acre, the yield per acre of marketable pota- 

 toes from the sprayed being 310 bushels 12 

 lbs. per acre, and from the unsprayed 189 

 bushels 54 lbs. The cost of the bluestone, 

 which is the principal expense, was $7.98 

 per acre, or 114 lbs. at 7 cents per lb. In 

 spraying large areas the cost would be less. 

 At 40 cents a bushel, an increase of 120 

 bushels per acre would mean $48, or after 

 deducting the cost of the bluestone, about 

 $40.00. 



The object of spraying is to destroy the 

 spores of the disease on the foliage. If the 

 mixture is not there when the spores are 



there the disease will usually spread very 

 rapidly and soon the tops are destroyed. 

 The foliage should be kept covered with the 

 n.ixture from the middle of July, when the 

 spores may be expected to appear, until the 

 end of the season, and from four to five 

 sprayings will be found necessary. In 1902 

 the vines were kept growing 18 days longer 

 by spraying. The vines were sprayed on 

 July loth, July 22nd, July 30th and August 

 13th, and probably even better results would 

 have been obtained if another spraying had 

 been made. 



Formula for spraying to prevent potato 

 L light and rot : 



Copper sulphate (bluestone), 6 lbs. 



Unslaked lime, 4 lbs. 



Water, 40 gallons.* 



Dissolve the copper sulphate with hot 

 water or by suspending for several hours in 

 a coarse bag in a wooden or earthen vessel 

 containing four or five or more gallons of 

 water. Slake the lime in another vessel. 

 If the lime when slaked is lumpy or granu- 

 lar it should be strained through coarse 

 sacking or a fine sieve. Dilute the sul- 

 phate of copper solution to about 20 gallons, 

 and the lime mixture to about 10 gallons, 

 and then pour the latter into the former, 

 then dilute to forty gallons and stir the mix- 

 ture thoroughly. 



Stock solutions of copper sulphate and 

 lime at the rate of i lb. to i gallon of watei* 

 may be prepared and kept in separate cov- 

 ered barrels throughout the spraying season 

 and diluted and mixed when needed. 



While the potato beetles are active, 8 oz. 

 of Paris green should be added to each 40 

 gals, of the Bordeaux mixture. The mixture 

 should be applied by means of a spray pump 

 with a good nozzle in order to get a fine 

 spray, which is necessary to get best results. 



