SOILSTAIN, OR SCURF, OF THE SWEET POTATO 1 
By J. J. Taubenhaus, 2 
Associate Plant Pathologist , Delaware Agricultural Experiment Station 
INTRODUCTION 
Soilstain of the sweet potato (Ipomoea batatas) is a disease which is 
little known. The present work is the result of three years' investigations 
by the writer. 
The disease was first described by Halsted (3) in 1890 under the name 
“scurf.” For the last 24 years nothing new has been added to our knowl¬ 
edge of this trouble; subsequent writers have merely quoted. Halsted. 
From the writer's studies (8, 9) it became evident that the disease needed 
further elucidation. The average grower little suspects that “stain” is 
a fungus trouble. In fact, the term “soilstain” as applied by the grower 
indicates his belief that there is something in the soil which stains the 
roots. He even believes that the plant itself leaves some coloring matter 
in the soil which stains subsequent crops of this valuable root. Others 
think that the staining is due to the application of manure to the soil; 
hence, they term it “manure stain.” 
ECONOMIC IMPORTANCE OF THE DISEASE 
Soilstain is not a disease to be feared in the sense that it may produce a 
direct rot in the mature roots; nevertheless, it is economically important. 
Growers whose lands are badly infected assert that stained roots keep 
better in storage. Others find consolation in saying “there is no such 
thing as stain, the dark color of the skin being merely a varietal charac¬ 
teristic.” The fact remains, however, that many eastern markets dis¬ 
criminate against stained roots. In years of overproduction the New 
York market refuses stained roots. The western buyers, on the contrary, 
are lax on this point; otherwise, many growers in the United States 
would be forced to cease producing sweet potatoes for want of a market. 
OCCURRENCE OF SOILSTAIN 
Soilstain is prevalent in Delaware on practically all sweet-potato land. 
It has also been reported from other States where sweet potatoes 
are grown. The writer has met with it in the sweet-potato districts of 
Delaware, New Jersey, Maryland, and Virginia. 
1 The Editorial Committee of the Journal of Agricultural Research kindly forwarded to the writer a copy 
of Harter’s paper on "Sweet-Potato Scurf” before it was published, with the suggestion that reference to 
that article be made. The writer has covered certain studies on the scurf of the sweet potato in storage and 
has treated more fully the morphology and physiology of the fungus than has Harter. These studies verify 
the work of Harter with one exception; in the morphology of the fungus he overlooked the fact that the 
conidia are catenulate. 
2 The writer is indebted to Dr. Charles Thom, of the Bureau of Chemistry, and Mrs. Flora W. Patterson, 
of the Bureau of Plant Industry, for having examined specimens of this fungus. 
Journal of Agricultural Research, Vol. V, No. 21 
Dept, of Agriculture, Washington, D. C. Feb. ai, 1915 
bz Del.—1 
(99s) 
22534°—16-4 
