A STUDY OF BACTERIAL PUSTULE OF SOYBEAN, AND A 
COMPARISON OF BACT. PHASEOLI SOJENSE HEDGES 
WITH BACT. PHASEOLI EFS. 1 • 
By Florence Hedges 
Assistant Pathologist, Laboratory of Plant Pathology, Bureau of Plant Industry, 
United States Department of Agriculture 
INTRODUCTION 
In the fall of 1916 badly spotted 
soybean leaves were received from 
Texas. The leaves were thickly cov¬ 
ered with small, brown, angular, slightly 
raised spots (PI. 2 A), from which a 
yellow organism resembling Bacterium 
phaseoli EFS. was isolated, and inocu¬ 
lations with this produced the disease 
on healthy soybean plants. The same 
disease was observed by Erwin F. 
Smith in 1902 on leaves from Charles¬ 
ton, S. C., and by the writer in the 
Dismal Swamp, Virginia, in 1917. In 
both cases an organism like Bacterium 
phaseoli was isolated. In later years 
it has been received from other 
localities. 
HISTORY OF THE DISEASE 
The first mention in literature of this 
■disease is a brief note by Smith(17) 2 in 
1904; and the leafspot referred to by 
the same author in “ Bacteria in Rela¬ 
tion to Plant Diseases” {18, v. 1, p. 92; 
v. 2, p. 69) is the one here under dis¬ 
cussion (oral communication), but no 
description of the disease or organism 
was given. Heald {6, p. /+1, 71) in 
1905 and again in 1906 (7) described 
very briefly a bacterial blight of soy¬ 
bean, but no cultural studies were 
made and it is impossible to tell with 
certainty whether the disease which 
came under his observation was the 
one discussed here or the leafspot 
described by Johnson and Coerper 
{10, If), resembling the pustule disease 
in certain stages but caused by a white 
organism. Bad. glycineum Coerper, or 
whether it was the one attributed by 
Wolf {22) and Shunk {Ilf to Bad. sojae 
Wolf, which resembles Bad. glycineum 
so closely that it is questionable 
whether one or two diseases are 
involved. 
Clinton {3, p. 444 ~ 44 />) in 1915 gave 
a more detailed description of a bac¬ 
terial leafspot of soybean and con¬ 
sidered it identical with the bacterial 
disease of wax and Lima beans and due 
to Bad. phaseoli EFS., but made no 
cultural studies. Bryce {2) in 1917 
reported the occurrence in Canada of a 
bacterial blight of soybean leaves, but 
accompanied this statement with no 
description; and the Plant Disease 
Survey of the United States Depart¬ 
ment of Agriculture {5, p. 116) recorded a 
bacterial leafspot on soybean in Penn¬ 
sylvania and Indiana in 1918, with no 
clue as to which bacterial disease was 
meant 
Three other species of bacteria are 
known to be infectious to soybean in 
the United States: Bacillus lathyri 
Manns and Taubenhaus {11, p. 12; 
21, p. 141), Bad. solanacearum EFS. 
{19), and Bad. flaccumfaciens Hedges {8), 
but there is no danger of confusing any 
of the diseases caused by these organisms 
with the one under discussion. 
In 1902, Smith isolated from soybean 
leaves the yellow bacterium resembling 
Bad. phaseoli EFS., and reproduced 
the disease on healthy plants by pure 
culture inoculations. Infections re¬ 
sembling those caused by Bad. phaseoli 
EFS. were also produced on varieties 
of Phaseolus sp. But, although several 
attempts were made, no infection with 
very virulent colonies of Bad. phaseoli 
EFS. isolated from Phaseolus was ever 
obtained on soybean by Smith (oral 
communication). Thus the question 
as to the identity of the two parasites 
has long been an open one, and in an 
attempt to solve this problem the 
writer undertook the present work, a 
preliminary account of which has been 
published {9). 
GEOGRAPHICAL DISTRIBUTION 
Little is known in regard to the geo¬ 
graphical distribution of this disease. 
The writer has received material from 
Texas (1916), Virginia (1917 and 
1 Received for publication Apr. 19, 1924—issued January, 1925. 
2 Reference is made by number (italic) to “Literature cited,” p. 250-252. 
Journal of Agricultural Research 
Washington, D C. 
( 229 ) 
Vol. XXIX, No. 5 
Sept. 1, 1924 
Key No. G—440 
