Feb. 16,1924 
Physiological Studies on Flag Smut of Wheat 
427 
Miyake (10) reports the occurrence of flag smut in China and states 
that it is “ very common in Peking and its vicinity.” 
Putterill (12) reports the occurrence of flag smut in South Africa, 
and states that it probably has been present there for a “number of 
years,” and that “while the total loss up to now may not be considered 
very great in that district [Marico], yet in some wheat fields lately 
visited almost half of the crop was found to be affected.” 
Flag smut of wheat was collected by E- C. Stakman in 1922 at Rieti, 
Italy, and at Zaragossa, Spain. The economic importance in either 
country was not determined. 
SYMPTOMS OF THE DISEASE 
The first indication that a plant in the field is infected with flag smut 
is the appearance of long grayish-black stripes running parallel with the 
veins on the upper leaves. At this stage diseased plants in the field 
appear to be as vigorous as the healthy ones. At a later stage the 
leaves and upper part of the culms become twisted and curled. Upon 
close examination of infected plants grown in the greenhouse and field it 
was found that the young upper leaves showed stripes which were white 
at their base, becoming whitish gray and finally a lead-gray in color 
toward the apex of the leaf. Later the epidermis of the leaf ruptures 
along these stripes and exposes the spores of the fungus in black sooty 
masses. Plate 1, A, shows some infected leaves with the typical sori. 
An enlarged portion of an infected leaf also is illustrated (PI. 1, B). 
The stripes, or sori, generally are confined to the leaves, although they 
may occur frequently on the leaf sheaths (PI. 1, C), occasionally on the 
upper part of the culm, and still more rarely on the lower glumes and 
rachis of the wheat head (PI. 1, E>). Plate 1, C, shows the infection 
occurring on the lower glumes of an underdeveloped head. In many 
cases all the culms of a diseased plant are infected, although an occasional 
plant in the greenhouse or field may be found with but one infected culm 
and the others apparently free from the disease and producing well- 
filled heads. 
In general, the disease seems to stunt the growth of the culms so that 
no heads are produced. However, in the field in 1922 and 1923 cases 
were noted where the smutted culms apparently were producing normal 
heads. These, upon examination, were found in many cases to be 
sterile, though occasionally a few seeds in each head matured. . McAl- 
pine (9) has noted cases where small amounts of shriveled grain were 
produced from infected culms. In a few of these individuals producing 
sterile heads it was noticed that the infection was confined entirely to 
the upper part of the culms, there being no infection of any of the leaves 
of that culm or of the remainder of the plant. 
In the greenhouse, plants of some varieties of spring wheat become 
infected before they begin to tiller. Very susceptible winter varieties 
also become infected before or at about the time they begin to tiller. 
Infection may appear at any time from these young stages of devel¬ 
opment until the plants are mature. 
The culms of infected plants grown in the greenhouse do not tend to 
curl and twist, as commonly is the case in the field. Infected plants 
were not allowed to mature, which fact might account for the difference 
in the effect on plants grown in the greenhouse and on those in the field. 
It was noticed, however, that in certain varieties, such as Hard Federa- 
