SWEET-POTATO SCURF 
By L. L. Harter, 
Pathologist, Office of Cotton and Truck Disease Investigations , 
Bureau of Plant Industry 
INTRODUCTION 
The scurf disease of the sweet potato (Ipomoea batatas) was first 
described by Halsted, 1 who published a brief account of it in 1890. To 
the fungus he gave the name Monilochaetes inf us cans, a new genus and 
species, of which, unfortunately, he gave no technical description. 
For many years following his pioneer work little or no attention was 
given to sweet-potato diseases. This very common and interesting dis¬ 
ease was therefore passed over until a few years ago, when the writer 
and others took up a study of them. For almost five years the disease 
has been under observation and study. It is therefore for the purpose of 
completing the description of the organism and recording the results of 
inoculation experiments and certain characteristics of the fungus here¬ 
tofore unpublished that this paper is prepared. 
GENERAL APPEARANCE OF THE DISEASE 
Scurf is characterized by a brown discoloration of the surface of the 
underground parts of the sweet potato (PI. EVII). The discolored areas 
may occur as spots of varying size and shape, with no definite outline, or 
as a uniform rusting of the entire surface. In gross appearance it re¬ 
minds one somewhat of the silver scurf of the Irish potato, although it is 
somewhat darker. However, it does not penetrate the host to the 
extent that silver scurf does. The scurf of the sweet potato produces 
no rupture of the epidermis and is so superficial as to be easily scraped 
off by the finger nail. 
DISTRIBUTION, PREVALENCE, AND LOSS 
The writer has found the scurf very prevalent on sweet potatoes in 
New Jersey, Delaware, Maryland, Virginia, North Carolina, Ohio, Illinois, 
Iowa, and Kansas, and to a slight extent in other States. The following 
varieties are susceptible to scurf in varying degrees: Eclipse Sugar Yam, 
General Grant Vineless, Florida, Nancy Hall, Yellow Yam, Miles Yam, 
Red Brazilian, Dahomey, Yellow Strasburg, Pierson, Key West Yam, 
Vineless Yam, Southern Queen, Big Stem Jersey, Yellow Jersey, and 
Early Carolina. It is probable that the disease occurs on other varieties 
as well. 
1 Halsted, B. D. Some fungous diseases of the sweet potato. N. J. Agr. Exp. Sta. Bui. 76, p. 25-27, 
fig. 17. 1890. 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
bw 
(787) 
Vol. V, No. 17 
Jan. 24, 1916 
0-73 
