Mar. io, 1923 
Rosette Disease of Wheat and Its Control 
779 
evidence that winter conditions do influence the development of the 
disease, there is no evidence that winter conditions are the prime cause. 
While the disease was first reported after an unusually mild winter, it 
has recurred each spring since that time. In this 3-year period, two 
mild winters and one severe winter have occurred, as shown in figure 1. 
This figure shows the average monthly mean temperature curve for 
the 10 years previous* to 1918 and the monthly mean temperature curves 
for the past 3 winter seasons in the vicinity of Granite City, Ill. These 
curves are based upon the daily temperature records published by the 
United States Weather Bureau at St. Louis, Mo. 
Fig. i. —Graph showing monthly mean temperatures in degrees Fahrenheit for the six winter months in 
the years 1918-19, 1919-20, and 1920-21, compared with the 10-year average temperature in the same six 
months. The winters of 1918-19 and 1920-21 were unusually mild. 
During the winters of 1918—1919 and 1920-1921 there was very little 
snow cover, and, as shown by the curves (fig. 1), these seasons were above 
normal in temperature. During the. winter of 1919-1920, however, the 
opposite was true. 
These data, together with the results from soil sterilization experi¬ 
ments discussed under Parasitic Factors on page 783, show that weather 
conditions in themselves are not the direct cause of the rosette disease. 
SOIL CONDITIONS OTHER THAN PARASITIC 
The rosette disease has been found to occur on all types of soil from 
a poor sand to a reasonably fertile gumbo, and under all conditions of 
soil drainage. 
From the beginning of these investigations these factors were not con¬ 
sidered very promising possibilities as primary causes of the disease; 
