STUDIES IN BACTERIOSIS. 



1. "BLACKLEG" OF THE POTATO. 



By SYDNEY G. PAINE- 



{From the Department of Plant Physiology and Pathology, 

 Imperial College of Science and Technology, London.) 



INTRODUCTION. 



The losses caused by bacteriosis of the potato in this country are 

 fortunately not so great as they appear to be in other parts of Europe, 

 the United States, and in Canada. Compared with fungal diseases 

 those of bacterial origin are quite of secondary importance and do not 

 usually cause any serious trouble. In most districts a certain number of 

 plants succumb each year to attacks of bacteria but they are so few that 

 very little notice is taken of them, they are usually pulled up and burnt, 

 but sometimes are left standing in the field without detriment to the 

 neighbouring plants. The chief losses are incurred during storage in 

 the clamp or pie, and unless special precautions to insure a good 

 system of ventilation are taken in building the clamp the conditions 

 of warmth and moisture may become so favourable to the growth 

 of bacteria that a few diseased tubers included in the crop act as foci 

 from which disease spreads. In this way the whole, or a large part, 

 of the store occasionally becomes involved. If on any field a more 

 than usual number of plants showing signs of bacterial disease are 

 noticed during the summer the wise man takes the precaution not to 

 store the crop from this field but to send it at once to market. 



Epidemics are of such rare occurrence in this country that the 

 subject has received but little attention by English pathologists. In 

 Canada however the losses from this cause have assumed much more 

 serious proportions, Harrison (6) found the average percentage of rotted 

 tubers during three years as high as 22 per cent., and the report of the 

 crop correspondent of the Canadian Bureau of Industries for 1905 



