Vegetable Growing for Market 



153 



spread upwards from the tubers, thus preventing the rise of the sap and 

 causing the stems and leaves to "flag" or wilt (fig. 486). As a rule the 

 leaf -curl disease causes the tubers to remain hard and firm, and prevents 

 the natural fermentation for proper growth. Perhaps the best remedy 

 against this disease is to obtain immature or at least not over-matured 

 "seed"; to sprout all tubers before plant- 

 ing; and to dress the deeply dug ground 

 with slaked lime or chalk about J bus. 

 to 1 rod if much stable manure has 

 been used. 



Mr. W. P. Lashain (Messrs. Button & 

 Sons' potato expert at Heading) is 

 strongly of opinion that Potato Curl is 

 due to over-maturing of the seed, be- 

 cause scarcely a crop grown from Scotch 

 vseed suffers from the disease. He has 

 always found that immature seed did 

 not suffer from " curl ". In the case of 

 mature or over-mature seed, the old set 

 is found nearly always as sound as 

 when planted. This is never the case 

 with immature seed. Mr. Lasham thinks 

 that there is not sufficient moisture in 

 mature seed to enable the tuber to decay 

 quickly enough to yield its nourishment to the sprouting stems and root 

 fibres. 



Potato Scab. This is caused by Oospora scabies, a fungus that usu- 

 ally attacks the young tubers, forming scattered roughish patches or scabs 

 on the surface, sometimes spreading all over. To prevent this disease 

 from spreading, only healthy uriscabbed tubers 

 should be planted, arid the ground should be 

 deeply dug and allowed to sweeten by ex- 

 posure to the atmosphere before planting. If 

 too much stable manure has been used, lime 

 should be added to rectify it; or if too much 

 lime has been used (as is sometimes the case), 

 then well-rotted stable manure may be dug 

 in the previous autumn or early in spring. 



Black Scab OP Warty Disease. This is 

 also known as Canker and Cauliflower dis- 

 ease (fig. 487), the latter name arising from the fact that large irregu/ar, 

 crested, or mossy outgrowths, like pieces of dirty Cauliflower heads, are 

 produced on the tubers. This disease is caused by a fungus, Synchitrium 

 (Chrysoplilyctis) endobioticum, and is more prevalent in some districts than 

 in others. It first appears in the form of warts or wrinkles near the eyes 

 of the young tubers, and later on several of these warts, growing together, 



Fig. 486. Potato Leaf Curl Disease 



Fig. 437. -Black Scab or Warty Disease 

 of Potatoes 



