A BACTERIAL BLIGHT OF GLADIOLI 1 
By Lucia McCulloch 
Assistant Pathologist , Laboratory of Plant Pathology , Bureau of Plant Industry , United 
States Department of Agriculture 
INTRODUCTION 
In the summer of 1922 a disease that was causing serious injury to 
the leaves of gladioli was reported by a large grower of these plants in 
the Middle West. The disease if present at all in previous years had not 
attracted attention. 
In 1923 in the same fields, and especially in poorly drained areas, 
the disease appeared on some young stock and a large number of these 
plants were destroyed. However, the infection abated rather suddenly 
and caused no further damage. Occasional cases of infection were 
noted on the older stock. 
In early September (1922) when the affected fields were examined 
by the writer, the leaves had a distinctly burned appearance. Closer 
observation showed them to be variously spotted, browned and ragged. 
Many leaves were heavy and stiff with adhering soil particles. 
Young stock appears to be much more susceptible to this disease 
than mature plants. Of 16 varieties studied in the field, the young 
stock of 15 varieties was severely attacked, while mature plants of the 
same varieties showed only slight spotting or no infection. One exception 
was noted, mature plants of the variety Schwaben were nearly as badly 
infected as the young stock. On the contrary, no trace of this disease 
was found on either young or mature plants of the variety Mrs. Frank 
Pendleton, although these were growing in the same fields and under the 
same general conditions. 
Microscopic examination of the discolored areas on the leaves revealed 
great quantities of bacteria in the tissues. 
In a search through the literature of.plant diseases, no description 
has been found that resembles this blight of the gladiolus and at present 
this mid-west farm is the only locality known to the writer where the dis¬ 
ease occurs. But since it is a serious menace to gladiolus culture and may 
be present elsewhere, it seemed worthy of further investigation. Careful 
observations were made in the fields and considerable material was 
collected for study. During the succeeding months experiments on plants 
in greenhouses and in outdoor beds and studies in the laboratory have 
established the following facts concerning the disease. 
Lesions are first visible as narrow, horizontal, water-soaked spots 
(PI. 1, A); the later progress of the infection is mostly in a longitudinal 
direction so that the spots become more or less regularly formed squares 
or rectangles (PI. 1, C and E). Adjoining lesions unite until often the 
entire leaf from the tip to the base is involved. This widespread infection 
of the leaf is most noticeable in the young stock. All parts of the leaves 
of blooming stock are also subject to attack, but the infection is quite 
1 Accepted for publication Dec. 14, 1923. 
( 27 $\ 
Journal of Agricultural Research, 
Washington, D. C. 
w l. XXVII, No. 4 
n. 26, 1924 
No 
