2 BULLETIN 1361, U. S. DEPARTMENT OF AGRICULTURE 
convenient to make observations in these counties for mosaic leaf 
mottling. In the spring of 1925 the writer observed mosaic on 
winter rye growing in infested soil at Granite City, 111., and in 
similar soil which had been transported to Madison, "Wis., for ex- 
perimental purposes. What appears to be the same mosaic also was 
found by Dr. A. G. Johnson in winter rye growing as a cover crop 
in the orchards of the United States Department of Agriculture, at 
Arlington Experiment Farm, near Kosslyn, Ya. Microscopic exami- 
nations of mosaic-infected rye plants from all these sources have 
shown the presence of cell inclusions which are very similar to, if not 
identical with, those associated with wheat mosaic, as previously 
described. 2 
This mosaic has not been observed on spring grains, but it does 
develop to a limited extent on spring-sown winter wheat when the 
season is cool. 
This is the first mosaic disease known to occur on graminaceous 
plants in the central Corn Belt. The importance of the disease 
is difficult to estimate at this time. It manifests itself in several 
ways on wheat, depending upon the varieties. The greatest damage 
appears to be caused by the rosette condition which develops in cer- 
tain winter varieties. Although many varieties do not develop the 
rosette condition, most of these exhibit the mosaic phase, and in some 
cases this apparently causes considerable injury. Although the 
mosaic symptoms of this disease appear to be identical with those 
of corn and sugarcane mosaic, further studies are necessary to de- 
termine whether these diseases are caused by the same virus. 
DESCRIPTION OF WHEAT AND RYE MOSAIC 
This disease seems to cause all of the symptoms associated with 
the mosaics reported on other Gramineee. However, owing to the 
small size of wheat and rye leaves, the mosaic pattern is much 
smaller and less conspicuous than that on leaves of corn and sugar- 
cane. Careful observations have shown that mosaic mottling oc- 
curs on a very few wheat plants in the late autumn, but the disease 
is not abundant until the new leaves develop in the early spring. 
The mottling consists of irregular streaks, which vary in length and 
width and tend to follow the direction of the long axis of the leaf 
(figs. 1 and 2). In some cases mottled leaves show a light-green 
pattern on the normal green background (fig. 1, B and C). Fre- 
quently, however, the greater proportion of the infected leaves are 
of the lighter green color, making it appear that there is a dark- 
green pattern on a light-green background (fig. 1, D and E \ fig. 2, B) . 
In certain varieties the leaves frequently develop light-yellow pat- 
terns or irregular strips, as shown in Figure 1, F. It is not un- 
common to find mosaic mottling also on the leaf sheaths and glumes. 
As in the case of the mosaic diseases of many other plants, the 
mosaic of wheat causes stunting or dwarfing and excessive prolifera- 
tion in certain varieties. This condition, previously described as 
rosette, causes a field to take on a spotted or patchy appearance 
on account of the various sizes of the areas which contain the 
2 H. H. McKinney, S. H. Eckerson, and R. W. Webb. Op. cit. 
