THE CULTURE OF POTATOES* 



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



One may keep potatoes growing thriftily 

 through a time of drought by thorough cul- 

 tivation and yet neglect looking after the 

 tops and preventing them from being de- 

 stroyed by the potato 'beetle and by the 

 blight and rot. Prof. Zavitz, in an experi- 

 ment at Guelph, showed that in an average 

 of two years potatoes which were allowed 

 to be eaten by bugs only yielded 60.69 

 bushels per acre, while those sprayed with 

 paris green yielded 138.20, an increase of 

 77.50 bushels per acre, and just in propor- 

 tion to the amount of top destroyed so much 

 wall the crop be lessened. Instead of wait- 

 ing until the vines begin to show very plainly 

 the work of the young beetles the vines 

 should be 'sprayed just w'hen they are hatch- 

 ing, as it takes a day or two^ usually before 

 the Paris green takes full effect and the vines 

 by that time are pretty badly eaten. 



Not only should we spray to kill the pota- 

 to beetle, but also to prevent the blight which 

 causes such great loss every year. If grow- 

 ers would only spray their potatoes with 

 Bordeaux mixture their crops would be very 

 miuch increased. In an experiment during 

 1904 with 15 varieties it was found that the 

 average yield per acre of the 15 kinds where 

 sprayed with Bordeaux mixture and Paris 

 green was 369 bushels 21 pounds per acre, 

 and the same varieties unsprayed 306 

 bushels 39 pounds per acre, or a difference 

 in favor of spraying of 62 busthels 42 pounds 

 per acre. Taking an average of three years, 

 the increase lias ibeen 94 bushels 30 pounds 

 per acre, which at 40 cents a bushel means 

 $39.80 per acre, the cost being about $9 per 

 acre at the outset for large areas, or a net 

 gain of $30.80. 



A combination of iiiordeaux miixture and 

 Bug Death gave an increase over ordinary 

 Bordeaux mixture and Paris green of 29 

 bushels 42 pounds per acre, but the cost oi 

 this was nearly twice as much as the former. 

 There was still, however, a net difference in 

 favor of Bus: Death and Bordeaux mixture 



applied together of $3.08 per acre, estimat- 

 ing the price of potatoes at 40 cents a bushel. 

 Bug Death applied alone in 1904 gave an in- 

 crease of only one bushel 13 pounds per 

 acre, taking an average of 15 varieties, al- 

 though with some varieties there was a 

 much greater difference, but on the other 

 hand with others there was about as great 

 a difference in favor of Paris green. It is 

 ortly by averaging that we can get at fair 

 estimates O'f what the results would be in 

 field culture. 



AN EXCELLENT MIXTURE. 



The best mixture of those which have 

 been tried for several years to prevent blight 

 and rot and to kill the potato beetle is the 

 poisoned Bordeaux mixture, the formula 

 found 'best by me being: Sulphate O'f cop- 

 per, 6 pounds ; lime, 4 pounds ; Paris green, 

 8 ounces ; water, 40 gallons. 



Although the blight does not usually ap- 

 pear until after the middle of July I prefer 

 using the Bordeaux mixture at the time 

 when the first spraying is made to destroy 

 the young beetles and keeping the vines cov- 

 ered with the iTiixture from then until Sep- 

 tember. In 1904 it took five sprayings to 

 do this. If the vines are not kept covered 

 it may happen that the blight will come un- 

 expectedly when spraying is needed. Hence 

 the work should be done thoroughly or not 

 at all. 



The first spraying we give is not con- 

 sidered necessary for the prevention of the 

 late Wight, but it does, we believe, protect 

 the foliage from other enemies. Five 

 sprayings should not cost more than $9 per 

 acre for time and materials if one has a good 

 spray pump. The Bordeaux-Bug Death 

 mixture which was tried this year for the 

 first time gave better results than Bordeaux 

 mixture and Paris green, but several sea- 

 sons' tests are necessary in order to show 

 whether it will average better than the Bor- 

 deaux mixture and Paris green. 



*C'^ntinued from the May issue. 



235 



