1922.] Potato Leaf Curl Demonstrations. 



1019 



Hams. — Very large and well filled to hocks. 

 Legs. — Short, straight and strong. 

 Colour. — White. 



Skin and Coat. — Smooth, hair straight, fine and silky, and not too much of it. 

 Size. — Large without coarseness. 



Disqualifications. — Black spots, black hair, prick ears. 

 Objections. — Blue spots. 



****** 



POTATO LEAF CURL 

 DEMONSTRATIONS. 



A. D. Cotton. 



Mycologist to the Ministry of Agriculture. 



It is well known (1) that potatoes affected with the disease 

 termed Leaf Carl or Leaf Roll suffer a very severe reduction in 

 yield, and (2) that it is by the use of infected seed that infected 

 crops with poor yields are produced. The necessity, therefore, 

 of using really good seed is clear. A large amount of very careful 

 research on potato diseases of this type has been carried out 

 during recent years, both in Europe and America, and the results 

 all emphasise (a) the necessity of preserving from infection plants 

 grown for seed-purposes, and (b) the immense importance to 

 growers of planting only absolutely healthy tubers. 



With the commendable object of saving expenses, growers are 

 often tempted to use home-grown seed instead of purchasing a 

 fresh supply from a good seed-area. If the crop is free from 

 disease, and especially from such troubles as Leaf Curl and 

 Mosaic,* this course cannot be objected to, but if the two 

 diseases mentioned are present, even in mild form, the resulting 

 crop will develop the same trouble, and the small weight of 

 tubers should show it to be false economy. Farmers are usually 

 more fully aware of the importance of good seed than the owners 

 of smaller holdings. The latter are only too ready 

 to blame the soil or the weather for a poor yield, whereas it is 

 commonly due to the use of infected seed. A walk round allot- 

 ments in any county of England will show that the " good seed " 

 lesson has not yet been learned. 



With a view to providing a practical demonstration of the 

 effect of Leaf Curl on the crop and the value of healthy seed the 

 Ministry instituted trials in various centres in 1921. In order 



° An account of these two diseases will be found in the Sectional Volume 

 No. 3 {Cultivation and Diseases of Potatoes^, price 8d., post free. 



