UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 879 
Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
Sl/&*&JU 
Washington, D. C. 
PROFESSIONAL PAPER 
November 15, 1920 
THE MOSAIC DISEASE OF CUCURBITS. 
By S. P. Doolittle, Assistant Pathologist, Office of Cotton, Truck, and Forage Crop 
Disease Investigations. 
CONTENTS. 
Page. 
Scope of the investigations 1 
The mosaie disease 1 
Cause of the disease 18 
Infectious nature of the disease 29 
Mosaic transmission 40 
Method of overwintering 47 
Control measures 63 
Summary 64 
Literature cited 68 
D 
SCOPE OF THE INVESTIGATIONS. 
UBJNG the last four years the more important diseases of the 
cucumber have been studied by various workers in coopera- 
tion with the Bureau of Plant Industry of the United States Depart- 
ment of Agriculture. One of the most significant facts developed 
in the early work was the occurrence of a mosaic disease, heretofore 
practically unrecognized, which is probably at the present time the 
y most widespread and destructive disease of cucumbers. The disease, 
however, is not confined to the cucumber but affects to a greater or 
less extent most of the cucurbits grown_in this country. 
The present bulletin deals with the nature, transmission, and 
overwintering of the disease in relation to cucurbits. The greater 
portion of the work has been done with the cucumber as grown for 
pickling purposes, in an attempt to develop field control measures. 
THE MOSAIC DISEASE. 
HISTORY. 
Although mosaic has been reported in the field and greenhouse for 
some years, it is only recently that the disease has received detailed 
attention. Selby (26) 1 in Ohio in 1902 and Stone (29) in Massa- 
chusetts in 1909 recorded a mosaic disease on the leaves of green- 
house cucumbers, and Clinton (8) in 1908 noted a chlorosis of musk- 
melon leaves in Connecticut. It is not certain, however, that all 
i The serial numbers in parentheses refer to " Literature cited " at the end of the bulletin. 
185118°— 20 1 
