STUDY OF THE LIFE HISTORY AND ECOLOGIC RELA¬ 
TIONS OF THE SMUT OF MAIZE 1 
By Alden A. Potter, formerly Assistant Plant Pathologist, Office of Cereal Inves¬ 
tigations, Bureau of Plant Industry, United States Department of Agriculture, 
and Leo E. Melchers, Plant Pathologist, Kansas Agricultural Experiment 
Station, and Agent, Office of Cereal Investigations, Bureau of Plant Industry, 
United States Department of Agriculture 2 
INTRODUCTION 
The smut of maize (Ustilago zeae 
(Beckm.) Unger) has proved much 
more difficult to control than any of 
the other cereal smuts. Although 
Arthur and Stuart ( 4 ?) 3 believed they 
had obtained control by fungicidal 
sprays, it has been generally accepted 
that there is no known practicable 
method of control. Neverthelesss, the 
current conception of the life history of 
the causal organism, drawn principally 
from Brefeld’s classic investigations 
(3, If), lends support to the idea that 
spraying might prevent the aerial 
conidia from producing infection. For 
this reason, further investigation of the 
ecology of the parasite, particularly 
with reference to the physiology anti 
morphology of the host, has seemed 
necessary in an effort to develop 
methods of control. The investiga¬ 
tions here reported cover the period 
from 1910 to 1920. Two brief ab¬ 
stracts have previouslv been published 
(U, 18). 
Referring to experiments conducted 
in Kansas in 1896, Hitchcock and Nor¬ 
ton ( 8 ) state, “the percentage of corn 
smut is here seen to rise to 26 per cent. 
This is, however, unusual; 6 per cent 
probably will represent the average.” 
Selby and Hickman (19) reported as 
high as 25 to 45 per cent smut in limited 
areas of a cornfield in Ohio, but gave 
4.4 per cent as the average infection. 
Pammel and Stewart (15) state that in 
Iowa only a fraction of 1 per cent of 
damage occurs for the entire state. In 
many Kansas fields, at the present 
time it is common to find 30 or 40 per 
cent of the plants affected with smut, 
while in the semiarid regions 60 to 80 
per cent are frequently noted. These 
percentages are based on plainly visible 
nodal, sheath, ear, and tassel infections, 
and do not include the less important 
galls on the leaf blades. A few years 
ago a field was found in Nebraska which 
showed virtually every plant affected. 
Difficulties have been encountered by 
investigators in recording observations 
on corn-smut infection in percentages. 
It is apparent that the less conspicuous 
galls on the leaves and sheaths of the 
corn plant have been overlooked or dis¬ 
regarded by some, while other investi¬ 
gators may have included such infec¬ 
tions in their reports. However, there 
appears to be sufficient reason for the 
belief that in the western part of the 
Corn Belt, at least, the disease has be¬ 
come much more prevalent during the 
last several decades. 
NATURE OF INFECTION 
Early observations made by the 
writers gave support to the statement 
of Pammel and Stewart (15) that the 
“lower nodes” are particularly subject 
to the disease and that on the same 
culm “where one smut boil made its 
appearance on the lower nodes, others 
appeared further up.” A fair example 
of the data obtained on this point 
involves notes taken on 3,500 plants at 
Mitchell, Nebr., in 1914. Twenty-six 
per cent of these plants showed infec¬ 
tion. This infection represented ap¬ 
proximately 4 per cent of the buds on 
3,500 plants, or 15 per cent of the buds 
on the infected plants. 4 Of this 15 per 
cent, 872 buds, or about 60 per cent 
of the infection, occurred on 372 plants, 
or 40 per cent of all plants showing any 
infection. In other words, 60 per cent 
of the total infection occurred on a 
little over 10 per cent of the total 
1 Received for publication Jan. 28,1924; issued April, 1925. Published with the approval of the Director 
as paper 191, Department of Botany and Plant Pathology, Kansas Agricultural Experiment Station. 
2 The authors wish to express their appreciation for the assistance given by Ira Flemming and Ivan A. 
White during the course of these experiments. 
« Reference is made by number (italic) to “Literature cited,” p. 173. . 
4 Counts were.made to include 10 buds per plant, beginning at the bottom and counting upward to a 
point one bud above the ear. 
Journal of Agricultural Research, Vol. XXX, No. 2 
Washington, D. C. Jam 15, 1925 
Key No. G-472 
13950—25f-5 
(161) 
