348 



STAtE BOARD OF AGRICULTURE. 



that the change in soil reaction was not brought about quickly enough and 

 that the young tubers had become spotted before the change was brought 

 about. Although control by soil treatment was not obtained during the 

 first season's experimentation, the results have not been entirely discourag- 

 ing and the 1921 trials will be planned to remedy the defects of those of the 

 past season. The solution of the Scab problem will be of great value to the 

 potato growers in the limestone areas who at present can grow but one crop 

 of marketable potatoes on a given jDiece of land and must each year select 

 a piece of virgin soil for their potato fields. 



BLACKLEG. 



This disease is one of the most important potato troubles in the Upper 

 Peninsula. It is very widespread and during cold, wet seasons, which are 

 particularly favorable for the disease, the loss incurred through death of 

 hills in the field and rotting of tubers in storage runs high. Losses of from 

 25 percent to 75 percent of the crop are not uncommon, and in seasons of 

 comparative drought fields showing as high as 10 percent of Blackleg can 

 often be found. 



Fig. No. 19. Young potato plant affected with blackleg, showing characteristic blackening of stem. 

 This disease can also be recognized by the yellowing and wilting of the leaves. 



