JOMAL OF MCCIIORAL R ESEARCH 
Yol. XXXI Washington, D. C., August 15, 1925 No. 4 
STEAM AND CHEMICAL SOIL DISINFECTION WITH 
SPECIAL REFERENCE TO POTATO WART 1 
By N. Rex Hunt, Pathologist, and F. G, O’Donnell and Rush P. Marshall, 
Plant Quarantine Inspectors, Federal Horticultural Board, United States Be- 
parturient of Agriculture. 2 
INTRODUCTION 
Soil disinfection studies were begun in 1919 in order to find a 
method by which the potato-wart disease caused by Synchytrium 
endobioticum (Schilb.) rerc. could be eradicated from infected soil. 
At that time little was known of the susceptibility of important 
potato varieties grown in the United States or of the probable rate 
of spread of the disease. With a total known infected area of only 
about 100 acres in Pennsylvania, Maryland, and West Virginia (fig. 
1) largely in the mountainous coal-mining regions, treatment of the 
entire area would have been feasible if a cheap, effective method of 
treatment had been found and the disease had proved destructive 
to a large number of our commercial varieties. It should be borne 
in mind that any method of soil treatment that would kill the thick- 
walled wart sporangia would almost certainly be too expensive to 
use even on small outlying areas unless it insured actual extermina¬ 
tion of the wart organism—nearly perfect control would not justify 
such heavy expenditures. 
In order to determine the susceptibility of potato varieties and of 
related plants and to study the behavior of the disease in America, 
as well as to test possible methods of eradication, a field station was 
established at Freeland, Pa., in 1919 and work was carried on during 
that and several suceedmg years. 
Fortunately a majority of our commercial potato varieties seem to 
be immune or highly resistant to the potato-wart disease and the 
disease appears to spread rather slowly. Quarantines and the grow¬ 
ing of immune varieties in infected areas seem likely to eradicate 
the disease in time {20, 21 ). 3 Although a number of soil treatments 
were used with apparently entire success in the eradication experi¬ 
ments, the development of some fundamental principles underlying 
the successful use of heat and, more particularly, of chemicals in 
soil disinfection, and the presentation of the supporting data con¬ 
stitute the more important parts of this report. 
1 Received for publication June 6, 1924; issued September, 1925. 
2 These studies were made as part of a general cooperative project on potato wart between the Office of 
Cotton, Truck, and Forage Crop Disease Investigations, Bureau of Plant Industry, the Federal Horti¬ 
cultural Board, United States Department of Agriculture, Pennsylvania State College, and the Pennsyl¬ 
vania State Department of Agriculture. Authorship of Part II should be credited to Hunt and O'Donnell, 
of Part IV to Marshall. 
3 Reference is made by number (italic) to “Literature cited," p. 363. 
Journal of Agricultural Research, Vol. XXXI, No. 4 
Washington, D. C. Aug. 15, 1925 
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