Mar. 10, 1923 
Rosette Disease 0} Wheat and Its Control 
775 
Granite City, Ill. In 1920 the first signs of the disease became manifest 
on March 24, and by April 1 there was no question as to its presence. 
During 1921 observations were made on the experimental plots located 
near Granite City, Ill., and also on plots maintained by the Indiana 
Agricultural Experiment Station near Valparaiso, Ind. In 1921 the 
disease made its appearance at Granite City during the latter part of 
February. This early development doubtless was due to the fact that 
the winter had been unusually mild. The disease has not yet been 
detected with certainty in the fall. 
FIELD SYMPTOMS 
Shortly after spring growth begins diseased areas present a very striking 
contrast with healthy parts of the field. Such areas show up as rather 
definite patches which vary in size and shape (PI. 2). In some cases 
one diseased plant (PI. 3, A) may be found among plants showing no 
signs of the disease. Frequently patches are found which are made up 
of only a dozen or so diseased plants, but usually the patches are con¬ 
siderably larger than this, and most commonly range from 3 feet to 
20 feet or more in diameter. These patches sometimes are circular, but 
more commonly are irregular in outline. Where the disease is most 
destructive, more than 95 per cent of the area of the field may be infested. 
The marginal limits of diseased areas tend to be rather sharply defined 
in contrast with the rather undefined patching usually found in connec¬ 
tion with poor soil conditions. The spotting caused by the disease is 
independent of topographical variations, and frequently patches are 
found to cover both poorly drained dead furrows and adjacent well- 
drained land. In the diseased patches, plants which partly recover 
tend to ripen later than healthy ones, causing a striking green spotting 
in the fields at ripening time. During wet seasons weeds become 
abundant in the disease-infested spots. 
PLANT SYMPTOMS 
The first positive indication of the disease, as the latter is now inter¬ 
preted, consists in a retarding of the early spring development of the fall 
tillers. At this time no external lesions are consistently associated with 
the living tissues of the diseased plants (PI. 1, B). Occasionally Helmin- 
thosporium lesions have been found on the subcrown intemode. 9 As 
pointed out later, such lesions sometimes are discernible in the early 
spring on the dead sheaths of autumn leaves. 
In the course of about a week after the first appearance of the rosette 
disease, affected plants tend to develop a dark, rather bluish green color, 
and numerous secondary tiller buds and tillers develop. The develop¬ 
ment of these secondary buds and tillers takes place around the crown of 
the plant, in a manner somewhat analogous to the twig proliferations 
occurring in peach rosette as described by Smith (jj). The excessive 
number of tillers developed by diseased plants give them a characteristic 
rosette appearance. Table III gives results of tiller counts made on the 
healthy plants and plants affected by the disease. 
9 The term subcrown internode as used in this paper refers to the structure in the wheat seedling between 
the crown and the base of the coleoptile. Under ordinary conditions this internodal structure usually 
elongates to a greater or less extent. 
