Jan. 15,1917 
Blackleg Disease of Potato 
81 
In 1902 Van Hall (15) in Holland described a bacterial disease of the 
potato which was similar to that described in Germany by Frank. He 
named the causal organism “Bacillus atrosepticus” This will be con¬ 
sidered more in detail in the discussion of the organisms studied by the 
writer. 
From 1902 to 1906 Appel published a series of several papers (1-7) 
upon his studies of the Schwarzbeinigkeit as he had observed it in Germany. 
His most complete account of the disease and the description of the 
organism was published in 1903 (4). He expressed a view at that time 
that possibly more than one organism might be associated with the dis¬ 
ease and suggested that the term “ Schwarzbeinigkeit” should not be 
considered as applying to a specific disease but as descriptive of a patho¬ 
logical symptom. He also mentioned that not all organisms studied by 
him which were able to cause decay of the tuber were capable of pro¬ 
ducing the stem disease as well. However, he pointed out that the 
organism causing Schwarzbeinigkeit , which he studied, was probably 
identical with the one described by Frank. This appears to be the most 
generally accepted view, although Appel found it to be a bacillus. He 
published a fairly complete account of it and named it “Bacillus phy¬ 
tophthorus” Smith (33) has more recently repeated and extended 
Appel's studies, working apparently with his original culture, and his 
description of B. phytophthorus is the most complete one that we have. 
In a general account of potato diseases and the disease resistance of 
potatoes, Jones (19), in 1905, describes blackleg and summarizes his 
observations upon its occurrence in Europe. He mentions it as being 
found in Germany, Holland, Belgium, France, and England. 
In 1906 Delacroix (12) reported on the presence of the Schwarzbeinig¬ 
keit in France and compared the appearance of plants affected with the 
latter and those showing “brunissure.” He states that blackleg is 
primarily a disease of the late spring or early summer, while the malady 
caused by Bacillus solanicola, as a rule, appears in midsummer or early 
autumn. However, he says, in effect, that the exterior characters are 
such that one can hardly separate the two diseases by them. 
In the same year Johnson (18) stated that he had clear evidence of 
the existence of Bacillus phytophthorus as a general cause of “yellow- 
blight," blackleg, and potato tuber-rot in Ireland, but Pethybridge and 
Murphy (26) are quite inclined to doubt his evidence. 
Jones (20) records for the first time the occurrence of blackleg in the 
United States, also in 1906. The disease agreed in every respect with 
that which he had observed in Europe. This was in Vermont on a farm 
where he had been studying potato diseases for nearly 20 years and had 
not previously observed it. The seed tubers used for planting came 
from Maine. 
In 1906 Harrison (17) described a potato disease of the same type 
which he stated to be of wide distribution in Canada and of much eco- 
