A BACTERIAL BUDROT OF CANNAS 
By Mary K. Bryan 
Assistant Pathologist , Laboratory of Plant Pathology , Bureau of Plant Industry , United 
States Department of Agriculture 
INTRODUCTION 
The disease described in this paper was first observed by the writer 
in July, 1918, when the unsightly appearance of hybrid canna plants 
(Canna indica L.) in the public grounds in Washington (PI. 31) drew atten¬ 
tion to it. The most noticeable lesions at that time were large, irregular 
brown spots which caused distortions of the leaves. Close inspection 
showed that many plants were attacked to a greater or less degree; 
leaves of all ages were involved, and often young shoots were killed by 
the destruction of the bud. A microscopic examination of sections of 
diseased areas disclosed the presence of swarms of bacteria in the tissues; 
and, as no mention of the disease was found in literature, a definite 
investigation was undertaken. 
APPEARANCE OF DISEASED PLANTS 
This disease is essentially one of young tissues and moist conditions. 
This is evident from the virulence of the attack on buds as well as from 
the fact that infections make little headway on mature leaves. 
The spots on the leaves vary in size from minute stomatal infections to 
ragged, brown, irregular areas extending several inches along the blade, 
usually between midrib and margin (PI. 32, 33). Small stomatal infec¬ 
tions are found in great numbers near the margins of large spots or on 
leaves with no large lesions, and on mature leaves they do not develop 
further. On young leaves they enlarge into spots which tend to run be¬ 
tween the parallel veins, giving to the leaf a striped effect. This effect 
is continued in the uneven margins of large spots formed by the coalescing 
of small ones, where often a diseased strip between two veins runs an 
inch or more beyond the main diseased area into otherwise healthy tissue. 
Young infections and the advancing edges of larger spots are first water- 
soaked, then yellow, later becoming brown. In the early morning water- 
soaked streaks extend far beyond the yellow tissue. Old spots are dry, 
thin, and grey-brown, and by shrinking cause distortions of the leaves 
(PI. 32, 33). They show a dark, almost black, mottling or checkering, 
which is more plainly seen by transmitted than by reflected light, the 
Journal of Agricultural Research, 
Washington, D. C. 
xn 
(143) 
Vol. XXI, No. 3 
May a, 1921 
Key No. G-225 
