JOURNAL OF Aapnm RESEARCH 
Vol. XXVIII Washington, D. C., Apbil 26, 1924 No. 4 
STUDIES ON CURLY-TOP DISEASE OF THE SUGAR BEET 1 
By Eubanks Carsner, Pathologist , Office of Sugar-Plant Investigations , Bureau 
of Plant Industry , and C. F. Stahl, Assistant Entomologist , Office of Truck-Crop 
Insects , Bureau of Entomology , United States Department of Agriculture 
INTRODUCTION 
Curly-top 2 of sugar beets presumably was widespread before it was recognized 
as a distinct disease. It appears to have been confused at first with other 
diseases or other types of injury. The extensive losses in California, in 1899, 
referred to as the “California beet disease/’ “Western blight,” etc., led to its 
being recognized as a distinct and serious disease, and the following year a 
similar condition was determined as occurring in all of the Western States where 
sugar beets were grown. 
Linhart (9) 3 summarized the reports of several specialists with reference 
especially to California conditions. This report recorded the conditions of the 
areas infected but did not establish the cause or exact character of the injury. 
Townsend (19) described and figured curly-top. 
Ball (1) in the Annual Report for 1905 of the Utah Station announced the 
discovery of a causal relation between the feeding of the beet leafhopper and 
“curly-leaf” or “blight.” 
Smith (14) reported the severe outbreak of 1905 in California, stating that the 
injury was apparently physiological in character and possibly of the same general 
type of disease as tobacco mosaic. 
Ball (2) emphasized, by further observation, the fact that “curly-leaf” is the 
result of leafhopper attack. He suggested that the disease itself might be in the 
nature of gall formation. 
Wilhelmi (21) reported alkali injury as a possible cause of curly-top. 
Townsend (20) described curly-top from both the pathological and geographical 
standpoints; while reaching the conclusion that the disease was a distinct systemic 
disease, he concluded that as yet no satisfactory explanation of the cause had 
been found. 
Ball (3) adopted the name “curly-leaf” for the disease, reviewed the earlier 
work, and reported in considerable detail the relation of the sugar beet leaf¬ 
hopper and other leaf hoppers to this and other injuries to the host plants. He 
emphasized especially that the curly-leaf condition, though produced by 
the leafhopper, is not due to mechanical injury by the insect nor to loss of sap. 
He pointed out that, in the case of injury produced in plants by related species 
of leaf hoppers, the injury was apparently local in character; while in the case 
of the curly-leaf, the abnormal condition apparently spread from leaf to leaf, 
infecting the whole plant even though the leafhopper might have disappeared 
in the meantime. He also reported that the agency that caused curly-leaf was 
capable of remaining in the beet over winter, again producing the typical curly- 
leaf symptoms in the first leaves in the spring. He referred to the experimental 
production of “curly-leaf” in cages arranged jointly by himself and Prof. E. G. 
1 Received for publication Jan. 23, 1924. 
2 The name “curly-top” has been used in earlier publications of this Department. The question of the 
advisability of employing “curly-leaf” instead of “curly-top” as the common name of this disease has 
been referred to the American Phytopathological Society. 
3 Reference is made by number (italic) to “Literature cited,” p. 318-319. 
\ 
Journal of Agricultural Research, 
Washington, D. C. 
94527—24f-1 
Vol. XXVIII, No. 4 
April 26, 1924 
Key No. Q-384 
(297) 
