208 The Potato 



not only be able to secure better prices, but will increase 

 his own yields because of the use of better seed. The 

 time will not be long before the southern potato-grower 

 will demand seed tubers certified by some responsible 

 organization, and poor seed will find a market for table 

 stock or some other purpose. 



Not all the vines thought to be healthy in the field will 

 produce satisfactory seed tubers. There may be hills 

 among them that produce a small number of marketable 

 tubers, and these should be eliminated from seed stock, if 

 possible. However, this can be done only by digging 

 each hill separately and selecting tubers from desirable 

 hills, as explained in an earlier chapter. Growers should 

 do this whenever possible to improve their own seed, but, 

 to improve further the seed stock for sale, much can be 

 done by grading because of the small tubers, many of which 

 come from weak or diseased hills. Growers at planting 

 time should discard all rotted, bruised or badly scabbed 

 tubers, for these are not as satisfactory as healthy, smooth 

 ones, even when treated. 



Seed treatment to prevent disease 



Seed treatment as directed will destroy organisms living 

 on or anchored on the surface of the tuber. For this 

 reason, it is to be advised when such diseases as com- 

 mon scab, powdery scab, rhizoctoniose and black-leg are 

 troublesome. Treated tubers often give a better stand 

 because rot organisms, ordinarily saprophytic, found on 

 the surface of the tuber are destroyed. Treating the 

 seed also eliminates the danger of introducing disease 

 organisms into new soil or soil that has been freed from 

 them to a greater or less extent. Few growers have 



