60 POTATO DEVELOPMENT WORK IN WISCONSIN. 



because of their effect upon the appearance of the tubers, 

 indeed, the consideration would affect table and seed stock 

 alike, but also chiefly, because of the fact that the germs 

 of these diseases are carried on or with the tubers from 

 crop to crop. Thus one of the most important considerations 

 with the purchaser of seed stock is that it be free from disease. 

 Herein lies the peculiar opportunity for Wisconsin seed potato 

 growers. 



There are large areas of practically virgin soil in northern 

 Wisconsin especially suited to potatoes. These soils are at pres- 

 ent free from disease germs. The responsibility rests with the 

 potato growers to keep them free. This means to begin with 

 the use of disease-free seed in planting them. Especial caution 

 should be used in importing seed from the Eastern States arid 

 under no condition should foreign potatoes be used for seed. 

 But in spite of any precautions likely to be taken diseases will 

 gradually come in. As this happens, the important thing is to 

 recognize them promptly and by proper measures hold them in 

 check. 



In order to make these matters more definite, I will list the 

 diseases which are likely thus to be introduced or borne on pq- 

 tato tubers with such brief characterization as will help in 

 guarding against them. 



SCAB DISEASES 



Common scab. This is familiar to every potato grower. In 

 the older sections it has been so widely introduced that seed po- 

 tatoes secured from any such source are almost sure to bear the 

 germs. Once introduced, it may persist for years in the soil. 

 Fortunately, the germs are on the surface and easily killed by 

 disinfecting. There are various methods of doing this, but the 

 simplest and best is to soak the seed for two hours in a solution 

 of 1 pound of formaldehyde (or formalin) in 30 gallons of wa- 

 ter. 



Powdery scab is a European disease, similar to the common 

 scab in general appearance and effect, but unfortunately the 

 germs are not so easily killed. Since this does not occur in 

 Wisconsin as yet, every care should be taken to guard against 

 its introduction. 



Black wart, somtimes called Black Scab, is another European 

 Disease even more to be dreaded. It attacks the eyes and young 



