Dec, 17, 1917 
Bacterial-Blight of Barley 
627 
Ordinarily the effects of the disease are not serious enough to be very 
conspicuous, causing only water-soaked lesions on the glumes like those 
on the leaves, but usually with less exudate. Such blighting of the 
glumes does not destroy the grain as a rule, although the kernels may 
become discolored (brown) and more or less stunted or shrunken. The 
most important aspect of such attacks, which will be discussed in a later 
chapter, relates to the possible overwintering and distribution of the 
disease with such attacked kernels. 
COMPARISON WITH SIMILAR PREVIOUSLY DESCRIBED BACTERIAL 
DISEASES 
From the preceding description it will be noted that this bacterial- 
blight of barley bears some similarities to certain previously described 
bacterial diseases. There are also distinct differences. 
R&thay’s disease of orchard-grass, caused by Aplanobacter rathayii E- F. 
S., (jo, v.i,p. 171; v. 3 , p. 133-160) and O’Gara's disease of western wheat- 
grass, caused by Aplanobacter agropyri O’Gara (6, 7), both have a charac¬ 
teristic exudate which is yellow in color and is produced in much greater 
abundance than in the case of the disease on barley. While those dis¬ 
eases are most conspicuous on the inflorescences and upper leaf sheaths 
the disease on barley occurs chiefly on the leaf blades, with distinct lesions, 
first on the lower leaves, then progressing upward, and usually less prom¬ 
inently on the heads. Culm and head distortions occasionally occur with 
barley in a manner somewhat similar to those with Rathay’s and with 
O’Gara’s diseases. Futhermore, while the diseases of orchard-grass and 
western wheat-grass are caused by nonmotile organisms, the disease of 
barley, as will be brought out later, is caused by a motile organism. 
Manns's bladeblight of oats (4) is characteristically different, both as 
originally described and as observed by the writers, from the bacterial- 
blight of barley treated in this paper. While both diseases produce 
local infections in a somewhat similar manner, the bladeblight of oats, as 
far as noted by the writers, is commonly characterized by a rather wide, 
conspicuous, light-colored, halo-like margin about the lesions on the leaf 
blades, well shown by Manns (4, PL XIII, fig. 1 and 3). Characteristic 
lesions of this type have been produced on oats by inoculating with pure 
cultures of what the writers take to be Pseudomonas avenae Mann s, iso¬ 
lated from oats. Thus, the characteristic lesions on oats are distintly 
different from those on barley, as previously described, the light-colored, 
halo-like margin not occurring on the barley. The causal organisms are 
also different. P. avenae , as described by Manns and also as isolated by 
the writers, is white in culture, monotrichous, and pathogenic on oats. 
The writers find it nonpathogenic on barley. The causal organism of 
the disease on barley studied by the writers is yellow in culture, mono¬ 
trichous, and pathogenic on barley, but not on oats. The writers con- 
