JOPRNAL OF AGMCOLTORAL RESEARCH 
Vol. XXV Washington, D. C., July 14, 1923 No. 2 
TRANSMISSION, VARIATION, AND CONTROL OF CER¬ 
TAIN DEGENERATION DISEASES OF IRISH POTA¬ 
TOES 1 
By E. S. Schultz, Pathologist, Cotton, Truck, and Forage Crop Disease Investigations, 
Bureau of Plant Industry, United States Department of Agriculture , and Donald 
Folsom, Plant Pathologist, Maine Agricultural Experiment Station 
INTRODUCTION 
Progress in solving the well-known problem of degeneration in the. 
Irish potato, Solatium tuberosum L., has been comparatively rapid during 
the last decade. With this progress the apparent complexity of the 
problem has increased. Consequently the results of many investi¬ 
gators are needed and frequent reports from the various workers in this 
field are desirable. 
Of the many phases of the problem in question, the writers have 
restricted their efforts largely to those of the transmission, variation, 
and control of certain diseases causing degeneration. This paper both 
confirms the results of workers in other regions and also discloses hith¬ 
erto unreported principles that must be respected if control is to be 
attained ultimately. 
TERMS AND TECHNIC USED IN THESE STUDIES 
As pointed out by Quanjer (jp f p. 127)* it is desirable that those work¬ 
ing with degeneration diseases agree as to the meaning of terms em¬ 
ployed. As the same author also points out in referring to the English use 
of the term “ leaf curl,” this agreement has not been realized. The varietal 
modification of symptoms described by Quanjer {39, p. jjo), by Murphy 
(29, P- 34), and by the writers in this paper, makes it difficult to reach 
such an agreement in the use of terms until at least the same variety is 
used by different investigators for a study of the various diseases. Under 
this state of affairs it seems necessary first to define the terms to be used 
in this paper. Certain general methods of technic also will be described 
here to obviate repetition. 
Degeneration diseases of potato are here considered to be those trans¬ 
missible or infectious diseases which are perpetuated indefinitely by vege¬ 
tative growth and propagation, and of which no cause, either organic or 
inorganic, has been identified and demonstrated. They include maladies 
of which the etiology is not fully understood. Although intracellular 
1 Accepted for publication May 2, 1923. This paper is based upon investigations carried on as a coopera¬ 
tive project between the Office of Cotton, Truck, and Borage Crop Disease Investigations of the Bureau of 
Plant Industry, U. S. Department of Agriculture, and the Department of Plant Pathology of the Maine 
Agricultural Experiment Station. Unless otherwise indicated, the work was performed in northeastern 
Maine in the vicinity of Presque Isle. The order of arrangement of the authors’ names is not intended to 
indicate that one cooperating institution contributed more than the other to the results. 
8 Reference is made by number (italic) to “Literature cited,” p. 115-117. 
Journal of Agricultural Research, 
Washington, D. C. 
afl 
Vol. XXV, No. 2 
July 14, 1923 
Key No. G-318 
48108 — 23—1 
(43) 
