BULLETIN No. 174. 



BLACKLEG. 



A Bactkriai. Disease; of the Stem and Tuber oe the Irish 



Potato.* 



W. J. Morse. 



For the past three seasons the writer has had under observa- 

 tion a stem and tuber disease of the Irish potato in Maine which 

 in some respects presents rather grave aspects unless the growers 

 and shippers of seed potatoes, in that part of the country where 

 the disease has become estabhshed, take immediate and radical 

 measures to prevent its propogation and spread. In this connec- 

 tion it should be mentioned that it is only here and there that 

 the disease has as yet, assumed such proportions as to produce 

 appreciable loss in this territory, and then more frequently in 

 wet seasons or on low ground, but careful examination of fields 

 over a considerable portion of the potato growing area of the 

 state shows that this is a malady of much more general distri- 

 bution than was first supposed. 



Unfortunately, there is considerable reason to believe that the 

 disease is conveyed to the new crop by means of infected seed 

 tubers. While the majority of Maine's i8 to 20 million bushels 

 of potatoes are sold for table stock the seed trade with southern 

 states has, in the past fcsv years, reached such proportions that 

 it cannot be ignored. So far as can be learned, blackleg assumes 

 much more serious aspect in the states farther south, and this 



* Attention has been called to this disease in the following previous 

 publications of this Station. Bui. 149, p. 323 (1907) and Bui. 164, p. 2 

 (1909). It was briefly described on page 6 of a revised edition of a cir- 

 cular entitled "How to Fight Potato Enemies" (March 1908) and in 

 September 1908 a newspaper bulletin was issued which briefly described 

 the appearance, nature and cause of the disease and cautioned dealers 

 against shipping seed tubers from fields affected with this trouble. 



