Vegetable Growing for Market 149 



These figures may be taken as applying chiefly to late or main-crop varie- 

 ties of Potatoes. If the work of preparing the ground is done with the 

 spade or the fork it will be done much better than if the plough is. used. 

 Although the ground is got over more quickly by machinery than by hand 

 labour, it is a question whether it is not really the more costly method 

 of cultivation in the long run. The soil is never so well cultivated or kept 

 so clean with the plough and harrow as it is with the spade and the fork, 

 and the latter system has the additional advantage of giving more men 

 employment and of having them available for other kinds of work that 

 cannot be done by machinery. It will be noticed that while there is very 

 little difference in the total cost per acre between the two systems, there 

 is likely to be a vast difference in the results. With main-crop Potatoes, 

 planted 3 ft. every way, and earthed up north and south, in ordinary good 

 potato soil, a yield of 15 to 18 tons of "ware" potatoes may be anticipated 

 against the 5 or 6 tons obtained in the ordinary way. It will probably 

 be a long time before potatoes will be grown in field or garden in the 

 way recommended, as it is hard to kill established customs, no matter how 

 absurd they are proved to be; and the wasteful and extravagant "lazy-bed" 

 system of planting, still practised largely in Ireland, will no doubt hold 

 sway for some time to come. 



Potato Diseases. Of late years the diseases of Potatoes have attracted 

 considerable attention, so much, indeed, that it has become quite usual to 

 talk about various sprays and washes for eradicating or preventing them 

 instead of adopting better cultural methods. Diseases, of course, are 

 natural adjuncts to all living things, including Potatoes, but there is no 

 need to invite their appearance by neglecting the dictates of common sense. 

 It may be safely said that most of the Potato diseases are mainly due to 

 three causes, viz.: (1) overcrowding; (2) lack of sufficient lime in the soil; 

 and (X) absence of deep cultivation. Remedy these defects, and less will 

 be heard in the future of Potato diseases. The air and sunshine, for which 

 growers pay absolutely nothing, are the finest natural antidotes to disease 

 in the leaves and stems of Potatoes, while a well-worked soil containing 

 a, fair supply of lime or chalk in one form or another will do much to 

 prevent the diseases of the tubers. 



The grower, however, must be always on his guard against attacks, 

 and it is well that he should be acquainted with or be able to recognize the 

 various Potato diseases here described. 



The Common Potato Disease, or Potato Blight, is caused by a fungus 

 called Peronospora infestans (fig. 485). The spores of this fungus are pro- 

 duced in enormous quantities, and, being very minute, are easily blown 

 about by the w T ind from one place to another. The disease was discovered 

 in Boston, U.S.A., and also in Denmark and Norway between 1840 and 

 1842, and by 1845 and 1847 it had ravaged the whole of Europe, and 

 caused the great Irish Famine. 



The first signs of this terrible disease are small brownish or yellowish 

 blotches on the leaves; these blotches gradually increase in size, the 



