POTATO WILT, LEAF-ROLL, AND RELATED DISEASES. 37 



appearance of the disease was normal, but later harvests fell to 

 nothing. No reliable results are available in this country. Con- 

 flicting reports come from farmers in the Greeley section; but, as no 

 pathologist accustomed to the diagnosis of leaf-roll saw either crop, 

 the relative amount of disease in home-grown and outside seed 

 remains unknown. 



It seems a wise precaution to use only selected seed from such 

 sources as Minnesota and Wisconsin for planting next year where 

 leaf-roll occurred last season. It may be that the disease will not 

 appear on crops from home seed, but the chances are that it will. 



The introduction of new and more vigorous varieties affords a 

 still more hopeful means of ultimately controlling the situation. The 

 problem of finding the best source of seed is the most important one 

 now confronting potato growers in the region affected by these 

 troubles. What is needed are selected stocks, true to name, with 

 vigor unimpaired and free from disease. The present difficulty is 

 that it is almost impossible to find such potatoes in large quantities. 

 Where growers have made experiments with outside seed they have, 

 as a rule, made their purchases in the open market or from middlemen 

 who have filled their orders with uninspected stocks, for which reason 

 no conclusions can be drawn from any experiments to date. 



There is fortunately a movement to organize among potato growers 

 in the principal Northern States, and this is backed by their State 

 experiment stations in a way that should in time make a supply of 

 reliable seed available. 



It would be well to follow the example of Germany, where a 

 system of official inspection is being inaugurated, through which 

 growers and purchasers may be assured that the crop from a given 

 estate is free from leaf-roll. Such a certificate can be granted only 

 after an inspection of the growing crop. The importance of such an 

 inspection in midsummer by a representative of the purchaser or by 

 an official expert can not be overstated. It is entirely impossible to 

 determine the vigor and freedom from leaf-roll of a stock of potatoes 

 after harvest. 



The practical phases of such a system of seed inspection and 

 certification will be discussed more fully in a later publication. 



CURLY-DWARF. 



Under the name "curly-dwarf" there is to be differentiated from 

 the leaf-roll a peculiar disorder, characterized by a dwarfed devel- 

 opment of the potato plant, accompanied by a pronounced curling 

 and wrinkling of the foliage, which has been compared to Scotch 

 kale and Savoy cabbage. It is known in Germany as "Krausel- 

 krankheit." The accompanying illustrations from photographs 

 (Pis. X and XI) show the typical appearance of this disease more 

 clearly than the printed description. 



