JOURNAL OF AGMaHTOAL RESEARCH 
Vol. XI Washington, D. C., December 17,1917 No. 12 
BACTERIAL-BLIGHT OF BARLEY 
By L. R. Jones, Professor of Plant Pathology , A. G. Johnson, Assistant Professor 
of Plant Pathology t and C. S. Reddy, Assistant in Plant Pathology , University of 
Wisconsin. 
INTRODUCTION 
For several years especial attention has been given to diseases of 
barley (Hordeum spp.) by the Department of Plant Pathology of the 
University of Wisconsin. In 1912 a peculiar leafblight was observed 
at Madison, Wis., at first causing considerable damage in a plot of two- 
row Montana barley, later appearing on the adjacent common six-row 
varieties. The general symptoms indicated that it was a bacterial 
disease, and laboratory studies strengthened this judgment. The 
disease has recurred in the departmental plots each year since and has 
been observed elsewhere as well, but it was not until the summer of 1915 
that sufficient critical study could be given to justify publication. These 
field observations and laboratory studies show that this is a widespread 
disease, capable of producing economic loss, and is caused by a heretofore 
undescribed bacterial parasite. 
APPEARANCE OF THE DISEASE 
On The leaves. —The first evidence of the disease which has been 
noticed is on the young, green leaves in the form of small water-soaked 
areas which later enlarge. In nearly all cases the progress is chiefly 
longitudinal, the invasion being retarded or limited by the veins. Thus, 
the more prominent lesions may assume the form of somewhat irregular 
stripes which may extend in certain cases the full length of the blade 
and sheath, but are apparently terminated at the node. Only in rare 
cases has a lesion been found on the culm. The most vigorous develop¬ 
ment results when the invasion occurs along the midvein, owing appar¬ 
ently to the greater thickness and succulence of these parts. In such 
cases the striped development becomes most pronounced (Pi. B, 2). 
Sometimes two or more stripes may develop on a leaf, giving an appear¬ 
ance somewhat resembling the so-called “stripe disease” of barley caused 
by Helminthosporium gramineum ( 8 , 9). 1 In addition to these stripe¬ 
like lesions, which are the more common, blotchlike lesions may also 
occur. At times these may involve so much of adjacent leaf tissue as to 
cause the entire blade, or considerable portions of it, to shrivel and turn 
Reference is made by number (italic) to “Literature cited,” p. 643. 
Journal of Agricultural Research, 
Washington, D. C. 
Id 
(625) 
Vol. XI, No. i2 
Dec. 17, 1917 
Key No. Wis—9 
