642 
Journal of Agricultural Research 
Vol. XI, No. 12 
SUMMARY 
(1) Bacterial blight of barley is a widespread disease capable of pro¬ 
ducing serious loss and is caused by a heretofore undescribed parasite. 
(2) The lesions on the leaves begin as small water-soaked areas which 
enlarge to yellowish or brownish somewhat translucent blotches or 
irregular stripes. Similar lesions may appear later on the glumes. The 
chief injury, however, is apparently to the foliage. 
(3) A bacterial exudate may appear scattered over the lesions as tiny 
clouded droplets which harden into yellowish resinous granules or spread 
to form a grayish, flaky surface film. This exudate and the translucency 
of the invaded parts are characters distinguishing the bacterial blight 
from the Helminthosporium diseases. 
(4) This disease bears some resemblance to R&thay's disease of orchard 
grass, to O’Gara’s disease of wheat grass, and to Mann's blade blight of 
oats. It is, however, distinct from any of these. 
(5) Primary lesions may appear on seedling plants very early in their 
development and secondary lesions when the plants are 8 to 10 inches 
high. Later the disease spreads with increasing rapidity. 
(6) The disease has been found widely distributed from the eastern 
Mississippi Valley to the Pacific coast. It attacks the barleys of all three 
of the main groups: viz, two-row, common six-row, and erect six-row. 
Within each group there is a considerable range of varietal susceptibility 
and, so far as observed, some are free from attack, but further work is 
necessary for final comparisons. 
(7) The invaded tissues and exudate are teeming with the bacterial 
parasite which has been isolated not only from these sources but also 
from dry overwintered leaves and from grain 2 years old. The organ¬ 
ism is a monotrichous rod, yellow in culture, with the group number 
211.2222532 and described as Bacterium translucens , n. sp. 
(8) Inoculation experiments have shown that the disease may be 
readily induced on barley by spraying with water suspensions of the 
organism. Negative results were obtained from inoculations on oats, 
rye, wheat, spelt, emmer, einkom, and timothy. 
(9) The channels of invasion are stomatal and intercellular. 
(10) Although the organism may overwinter in infected leaves, 
diseased kernels doubtless constitute the chief means of dissemination 
and source of spring infection. 
(11) While control measures are not as yet fully worked out, the most 
promising methods consist in the avoidance of infected seed and in seed 
disinfection. 
