ANGULAR LEAF-SPOT OF CUCUMBERS 
By Erwin F. Smith, Pathologist in Charge , and Mary Katherine Bryan, Scientific 
Assistant , Laboratory of Plant Pathology, Bureau of Plant Industry 
INTRODUCTION 
The angular leaf-spot of cucumbers (<Cucumis sativus) has been known 
in the field for many years, but up to the present time no organism has 
been named as its cause, though it has been generally conceded to be of 
bacterial origin. The disease is characterized by the formation of 
numerous, often confluent, angular, dry, brown spots which by drop¬ 
ping out or tearing give the leaves a ragged appearance. 
The literature on the subject, aside from mere notes on the occurrence 
of the disease scattered through pathological literature, consists of four 
papers by O. F. Burger, of Florida, 1 and a more recent Italian paper by 
Traverso. 3 Burger mentions the leaf-spot as preliminary to a more 
destructive fruit-rot, said to be due to the same organism. His descrip¬ 
tion of the diseased leaves agrees with the appearance of leaves sent to 
the writers from Wisconsin, as well as with those obtained by them 
from other States, and with the leaf-spots which they obtained in Wash¬ 
ington by pure-culture inoculations. A brief description of the causal 
organism is given in each of his papers, in one case with the group 
number according to the chart of the Society of American Bacteriologists. 
Burger’s descriptions agree in the main except as to flagella and the 
diameter of his organism. In his earlier descriptions it is said to have 
polar flagella, but in the later ones it is reported to be peritrichiate. 
No name is given to the bacillus. 
Traverso’s paper is only a preliminary one, but it leaves no doubt as 
to the identity of the Italian and American disease. A motile, fluor¬ 
escent, nonliquefying organism was isolated by him and inoculations 
were made with it, but no positive results were obtained (p. 459). 
Who first reported this cucumber disease in the United States is 
uncertain; the senior writer has known it for 20 years, and several years 
ago (1904) plated out two yellow bacteria with which unsuccessful 
inoculations were made. Again, in 1907, at his suggestion, Mr. John R, 
Johnston, then of the Laboratory of Plant Pathology, made platings 
1 Burger, O. F. A new cucumber disease. In Fla. Agr. Exp. Sta. Rpt. [1911J/12, p. c-ci. 1913. 
-A bacterial rot of cucumbers. In Phytopathology, v. 3, no. 3, p. 169-170. 1913. 
-Bacterial rot of cucumbers. In Fla. Agr. Exp. Sta. Rpt. [19121/13, p. xc-xdv, fig. 11-13. 1914. 
-Cucumber rot. Fla. Agr. Exp. Sta. Bui. 121, p. 97-109, fig. 37-42. 1914. 
2 Traverso, G. B. Sulla bacteriosi del cetriolo in Italia. Nota preliminare, Atti R. Accad, Idncei, 
Rend. Cl. Sci. Fis., Mat. e Nat., s. 5, v. 24, sem. 1, fasc. 5, p. 456-460. Apr. 5, 1915. 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
bl 
(46s) 
12571°—15 -2 
Vol. V, No. n 
Dec. 13, 1915 
G—68 
