BLACKLEG. 327 



to comply with these recommendations and all growers should 

 cooperate with them in their efforts to furnish stock free from 

 disease. 



Summary. 



Blackleg is a bacterial disease of the stem and tuber of the 

 potato. A similar appearing malady caused by bacteria has 

 been reported from Canada, and another from England, Ger- 

 many, France and other parts of Europe. Preliminary studies 

 of the organisms associated with the disease indicate that they 

 are closely related to those already described as a cause of 

 similar troubles elsewhere, but whether they are identical with 

 any of the described species of bacteria is not fully determined. 

 PP- 309-312. 



The attacked plants are usually unthrifty, light green or 

 even yellow, and undersized. The branches and leaves have 

 a tendency to grow upward forming a rather compact top, 

 often with the young leaves curled and folded up along the 

 mid-rib. The most characteristic thing about them is the inky- 

 black discoloration of the stem, at or below the surface of the 

 ground, but frequently running up the stem from one to sev- 

 eral inches above ground. The seed-piece from which the 

 attacked plants spring is invariably attacked with a soft-rot, 

 and the disease appears to start on the stem at its junction with 

 the diseased seed tuber. The germs of the disease are capable 

 of causing a rapid decay of the young tubers, and these are 

 sometimes attacked also. pp. 312-314. 



The evidence thus far obtained indicates that blackleg is 

 largely distributed by means of germs carried in wounds, cracks 

 and decayed areas of seed tubers. On account of the readi- 

 ness with which the organisms are killed by drying there is 

 little to fear from sound, smooth seed stock, but this should 

 be treated with a disinfecting solution as a matter of precau- 

 tion. There is some reason to think that blackleg was intro- 

 duced into Canada from England and from there to the United 

 States, pp. 314-318. 



Blackleg is apparently becoming quite widely distributed 

 throughout the Eastern part of the United States. In most 

 states it is not common enough to attract attention, and in no 

 region has it done much damage, although it may become a 



