JOmALOFAGRIdllMLESEARCH 



Vol. XVII Washington, D. C, September 15, 1919 No. 6 



INVESTIGATIONS ON THE MOSAIC DISEASE OF THE 



IRISH POTATO^ 



[PRELIMINARY PAPER] 



By E. S. ScHWtz,^ Pathologist, Cotton, Truck, and Forage Crop Disease Investigations, 

 Bureau of Plant Industry, United States Department of Agriculture, Donald Folsom, 

 Assistant Plant Pathologist, Maine Agricultural Experiment Station, F. MERRILL 

 HiLDEBRANDT, funior Chemist, and LoN' A. Hawkins, Plant Physiologist, Plant 

 Physiological and Fermentation Investigations, Bureau of Plant Industry, United States 

 Department of Agriculture 



INTRODUCTION 



The economic importance and wide distribution of the mosaic or 

 "calico" disease of tobacco (Nicotiana tahacujti L.), as well as its dis- 

 tinguishing characteristics, have been a matter of common knowledge 

 among pathologists and practical growers for many 3'ears. The fact 

 that mosaic occurs also on certain others of the Solanaceae is well 

 recognized, but it has been known for only a comparatively short time 

 that the Irish potato (Solanum tuberosum L.) is subject to a similar 

 malady. 



As will be shown, potato mosaic, although more common and appar- 

 ently more destructive in certain sections of the United States than in 

 others, is widely distributed in North America. While the data regarding 

 it which have so far accumulated are necessarily limited, there is a 

 tendency among those pathologists who have given the subject special 

 study to regard it as a disease of great economic importance. The 

 results of the studies described in this paper, chiefly those which throw 

 light on the means of transmission of the disease, are made more sig- 

 nificant by the fact that they were obtained in four different laboratories, 

 partly through collaboration and partly as the result of independent 

 work. 



' This paper was read at the conference of potato pathologists on Long Island, June 26, 1919. An abstract 

 was published in Phytopathology. 



The investigations were conducted as a cooperative project between the Office of Cotton, Truck, and 

 Forage Crop Disease Investigations of the Bureau of Plant Industry and the Department of Plant 

 Pathology of the Maine Agricultural Experiment Station. 



2 The authors wish to acknowledge their indebtedness to Dr. H. A. Edson and Dr. W. J. Morse for helpful 

 suggestions and criticism of the manuscript and to Dr. Joseph Rosenbaum, Mr. M. Shapovalov, and 

 Mr. G. B. Ramsey for assistance in furnishing material and collecting data. 



Journal of Agricultural Research, Vol. XVII, No. 6 



Washington, D. C. Sept. 15. 1919 



sg Key No. G-177 



(247) 



