44-8 
Journal of Agricultural Research voi. xxvii, No. 7 
SUMMARY 
Flag smut of wheat occurs in the United States, Australia, Japan, 
China, South Africa, Italy, and Spain. Although heavy losses have 
been reported from other countries, it has been estimated that in the 
five years that flag smut has been known in the United States there has 
been less than 2 per cent of loss in the infested areas. 
Flag smut of wheat is caused by Urocystis tritici Kcke., which produces 
sori on the leaves, stalks, and glumes. Badly infected plants do not 
head. The spores do not germinate readily in tap or distilled water, 
and special conditions are necessary for uniform germination. Spores 
kept under laboratory conditions were viable for at least four years. 
They are able to live through the winter in the soil in the vicinity of 
St. Louis, Mo. These overwintered spores are capable not only of ger¬ 
minating but of infecting wheat plants. 
Sowing inoculated wheat at successive dates in the fall at St. Louis, 
Mo., resulted in a general decrease in the percentages of infection. There 
was no infection in the sowing of November 14 or in later sowings. 
Infection occurred at 6° to 12 0 C., 17 0 to 19 0 , and 21.5 0 to 23.5 0 , but 
did not occur at 25 0 to 26.6°. The highest percentage of infection 
occurred at 21.5 0 to 23.5 0 . The most favorable stage of growth for 
infection was in the seedling stage before the coleoptile was broken and 
before the seedlings emerged from the soil. 
Infection occurred either earlier or in a greater percentage in a few 
varieties which had been inoculated and cut back at different stages of 
growth than in the same varieties which had not been cut back. 
Fulcaster, Poole, Red May, Red Rock, Early Defiance, and Galgalos 
remained smut-free during the three years of this experiment; Illini Chief, 
Treadwell, Turkey, and Peliss, grown for only two years, also were smut- 
free. The percentages of infection of susceptible varieties grown in the 
greenhouse were considerably higher than those of the same strains grown 
in the field. 
LITERATURE CITED 
(1) Brown, William. 
1922. STUDIES IN THE PHYSIOLOGY OF PARASITISM. IX. THE EFFECT ON THE 
GERMINATION OF FUNGAL SPORES OF VOLATILE SUBSTANCES ARISING 
from plant tissues. In Ann. Bot., v. 36, p. 285-300. Literature 
cited, p. 300. 
(2) Butler, E. J. 
1918. fungi and disease in plants. 547 p., illus. Calcutta. 
(3) Hecke, L. 
1907. die triebinfektion bei brandpilzen. In Ztschr. Landw. Versuchsw. 
Oesterr., v. io, p. 572-574. 
(4) Hori, Sh6tard. 
1901. [experiments for the prevention of flag smut of WHEAT.] In 
Tech. Rpt. H6koku Agr. Exp. Sta. no. 18, p. 6-9. (In Japanese.) 
(s)- r „ . _ 
1907. seed infection by smut fungi of cereals. In Imp. Cent. Agr. Exp. 
Sta. Japan Bui. 1, p. 163-176. 
1911. nosakumotsu byogaku [a discourse on diseases of crop plants]. 
Tokyo, Seibido 7 impr. M. 44, p. 153-157, fig. 17. (In Japanese. 
Not seen.) 
(7) Kornicke, F. 
1877. mykologische beitrage. In Hedwigia, Bd. 16, p. 33-40. 
(8) McAlpine, D. 
1905. flag smut of wheat (u. occulta). In Jour. Dept. Agr. Victoria, v. 3, 
p. 168-169. 
1910. the smuts of Australia. 288 p., 15 fig., 56 pi. Melbourne. Litera¬ 
ture, p. 205-212. 
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