UNITED STATES DEPARTMENT OF AGRICULTURE 
/dfiSxfiEsW 
In Cooperation with the 
Washington Agricultural Experiment Station 
DEPARTMENT BULLETIN No. 1239 
Washington, D. C. 
May, 1924 
STUDIES IN THE PHYSIOLOGY AND CONTROL OF BUNT, OR STINKING 
SMUT, OF WHEAT. 
By Horace M. Woolman, Field Assistant in Cereal- Disease Investigations, and 
Harry B. Humphrey, Pathologist in Charge of Cereal- Disease Investigations, 
Office of Cereal Investigations, 1 Bureau of Plant Industry. 
CONTENTS. 
Page. 
Physiologic factors affecting the develop- 
ment of bunt 1 
The problem of soil infestation 2 
Duration of viability of bunt spores 
in the soil ." ' 6 
Physiologic response of spores of Tilletia 
to temperature 8 
Relation of soil moisture to infection 11 
Morphologic response to pathologic condi- 
tions 12 
Relation of temperature to the germina- 
tion of bunt snores and wheat kernels. . 15 
Page. 
Control of bunt 18 
N ursery studies in seed treatment 18 
Relation of depth of seeding to bunt pro- 
duction -. 21 
Relation of rate of seeding to bunt pro- 
duction 23 
Breeding and selection studies of varietal 
resistance to bunt 25 
Summary 27 
Literature cited 28 
PHYSIOLOGIC FACTORS AFFECTING THE DEVELOPMENT OF BUNT. 
The studies reported here were carried on by the writers from 1913 
to 1921. Although these studies are by no means exhaustive it is 
believed that, in so far as they are conclusive, they will contribute 
materially to our knowledge of the relation of various factors to 
bunt infection, to the life history of the organism, and to methods of 
control of the disease. 
At the time the field experiments herein reported were begun at 
Pullman, Wash., it had become evident that the bunt of wheat in 
the principal wheat districts of the Pacific Northwest could not be 
controlled by seed treatment. Approximately all the wheat growers 
of this region were giving their seed as severe a treatment, following 
approved methods, as was possible without destroying its viability. 
In spite of this, 25 per cent of bunt was not uncommon and 50 per 
cent or more was sometimes observed. In general, the strength of 
i The research the results of which are recorded in this bulletin was conducted by the Office of Cereal 
Investigations of the Bureau of Plant Industry in cooperation with the Washington Agricultural Experi- 
ment Station. The writers wish to make s^ eial acknowledgment to Profs. F. D. Bealci and E. F. Gaines, 
of that, station, for their many helpful suggestions and to Dr. Erwin F. Smith, of the Bureau of Plant 
Industry, who made possible the soil temperature studies herein reported by placing at the disposal 
of the junior writer the special-compartment incubator of the laboratory under his care. 
Note.— This manuscript was submitted for publication October 8, 1923. 
78298—24 1 
