JOURNAL OF ACRICOLTORAL RESEARCH 
Vol. XXIX Washington, D. C., August 15, 1924 No. 4 
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A LEAF AND CORM DISEASE OF GLADIOLI CAUSED 
BY BACTERIUM MARGINATUM 1 
By Lucia McCulloch 
Assistant Pathologist, Laboratory of Plant Pathology , Bureau of Plant Industry , 
United States Department of Agriculture 
INTRODUCTION Several gladiolus farms in Central 
The disease caused by Bacterium 
marginatum probably occurs to some 
extent wherever gladioli are grown, but 
in some regions it does not attract much 
attention because the signs of disease are 
inconspicuous or entirely lacking. In 
other localities with more favorable 
conditions for the parasite, the loss may 
be considerable. The parasite in viable 
and pathogenic condition is carried over 
on the corms from season to season. 
The lesions being sometimes small, may 
escape detection; therefore corms ap¬ 
parently normal may be the means of 
carrying the disease to various parts of 
the country where, if conditions favor 
its development, it may become a men¬ 
ace to gladiolus culture. 
The bacteria causing this disease 
have been isolated from gladioli grown 
in Florida, California, Virginia, Penn¬ 
sylvania, Indiana, Michigan, Mary¬ 
land, and the District of Columbia. 
This disease was first studied by the 
writer in 1913 when a commercial 
grower in the Middle West sent to 
the United States Department of 
Agriculture a number of infected 
plants, and stated that the disease 
was causing considerable loss in his 
fields. From these plants an organism 
was isolated which proved to be defin¬ 
itely pathogenic and produced lesions 
on inoculated gladioli identical with 
those on the original host. The cul¬ 
tural characters of the organism were 
also determined at this time. 
In 1920 the disease was observed on 
gladioli growing in the District of 
Columbia and Virginia. Plants grown 
on the same land and from corms 
produced in 1920 were under observa¬ 
tion from 1921 to 1923 and all showed a 
recurrence of the disease. 
Michigan were examined by the writer 
in September, 1922, and the disease 
found generally prevalent but, accord¬ 
ing to the growers, it was less severe 
than in some previous years. 2 
A reference to laboratory notes indi¬ 
cated that an organism with similar 
characters was isolated from diseased 
gladioli received in April, 1910, from 
California. In July, 1922, the writer 
found inconspicuous lesions of this 
disease on gladioli in a florist’s shop in 
Los Angeles, Calif. The disease was 
not found at that time in the plantings 
about Los Angeles. 
A brief description of this disease 
and of the causal organism (Bacterium 
marginatum) was published in 1921 (1). 
In Phytopathology (2) there is an ab¬ 
stract of a paper read at the Cincinnati 
meeting. This abstract deals not only 
with the disease caused by Bacterium 
marginatum but also with another 
bacterial leaf blight of gladioli (8) 
caused by Bacterium gummisudans. 
DESCRIPTION OF THE DISEASE 
The lesions may appear on any part 
of the leaf but are usually confined to 
the fleshy, basal region, and it is here 
that the serious damage occurs. Tiny 
specks of bright reddish-brown color, 
slightly elevated and usually in con¬ 
siderable numbers, are the first visible 
signs of the disease. By enlarging and 
coalescing these spots produce large 
necrotic areas, in which all the paren¬ 
chyma tissue is destroyed (PL 1). 
When infections are more isolated, 
very typical lesions are produced. 
The tiny speck enlarges to a circular, or 
more often, elongated spot; the center 
is sunken, dark-brown, or almost black 
with the margin slightly elevated and 
1 Received for publication June 25, 1924—issued January, 1925. 
2 Thanks are given to H. C. Oven of Ovid, Mich., for cooperation in collecting specimens of diseased 
plants, supplying healthy corms for experimental purposes and for many helpful suggestions. 
Journal of Agricultural Research, 
Washington, D. C. 
Vol. XXIX, No. 4 
Aug. 15, 1924 
Key No. G-447 
