IOWA ACADEMY OP SCIENCE 
93 
THE LATE BLIGHT OP BARLEY (HELMINTHOSPORIUM TERES SAGC). 
BY A. L. BAKKE. 
INTRODUCTION. 
To the barley grower, no other disease of the barley is probably of such eco- 
nomic importance as the late blight iHelminthosporium teres). When active 
work was begun in the summer of 1909, certain barley plots of the college showed 
that more than 90 per cent of the plants*, in those plots were infected. The 
disease presents itself in the form of brownish, orange colored spots, which at 
first are oval or circular, but later become elongated. As a result of infection, 
the greater surface of the leaves takes on a yellowish color. In contrast to 
this effect is the brick red color of the spotted areas. A marked feature, as a 
result of an examination of a diseased plant, is that a single individual shows 
all stages of attack. Ordinarily the fungus is noticed in this locality, during 
the early part of July. Usually at that time, the basal leaves will have be- 
come completely dried, while those above will show a progressive decrease to 
the point w'here no spots are present. This disease is closely related to the 
'^Yellow Leaf.” The last named form is not so destructive for the reason that 
“Yellow Leaf” singles out individual plants, while the Late Blight is broadcast 
in its attack. 
HISTORY. 
Helminthosporium teres (Late Blight of Barley) has been known in Europe 
since 1881. It was found upon withered barley leaves near Padua, Italy, by 
Bizzazero and was diagnosed, named and described by Saccardo^^ as H. teres. In 
1889 Briosi and Cavara- described this same disease as occurring upon oats. 
P. Koplin Ravni2 in 1900 published the results of his extensive investigations 
in Denmark. Pammel in 1907 and 1908 observed the disease upon barley at 
Ames, Iowa. In June Pammel, King and Bakkeo, published the results of their 
observations for the season of 1909**. 
DISTRIBUTION. 
During the latter part of June, 1909, there was a reappearaiice of the spot 
disease of the barley, in the college plots, that had been observed by Pammel 
in 1907 and 1908. The fungus was observed during the summer of 1909 on 
barley fields of Minnesota** and Saskatchewan, Canada. Mr. A. G. Johnson of 
the Purdue Agricultural Experiment Station informed Pammel of the prevalence 
of a barley disease in the station plots of the South Dakota Agricultural Ex- 
periment Station during the season of 1909. He stated that one of the plots 
was practically destroyed. H. L. Bolley of the North Dakota Agricultural 
*Data furnished by Mr. Burnett showed that in many cases 100% were damaged by 
.the fungus. There was also considerable variation with different varieties. The 
varieties OderbrucheVj and Hulless were slightly damaged, but the varieties Primus, 
Hannchen showed 100% damage. Hanna showed 90% ; Manchuria 5%. 
**Bull. Iowa Agr. Exp. Sta. 116. 
