170 
Journal oj Agricultural Research 
Vol. XXX, No. 2 
might result from such spraying experi¬ 
ments, as to obtain confirmatory 
evidence in the study of the ecologic 
factors affecting the development of 
the corn-smut organism. These re¬ 
sults are briefly described below. 
THE POSSIBILITIES OF CONTROL 
In attempting a study of control 
measures, the following three general 
lines of procedure suggested themselves, 
namely, fungicidal treatments, cul¬ 
tural methods, and the development of 
resistant strains or varieties of corn. 
FUNGICIDAL SPRAYS 
The only experiments with fungicidal 
sprays which had been conducted up 
to 1910 when these investigations were 
begun, were those by Kellerman (10) 
in Kansas, and Stuart (20) and Arthur 
and Stuart (1) in Indiana. These 
early investigations, however, were not 
extensive and no record was made of 
the significance of the effect of the 
sprays on the corn crop, particularly 
the yield. 
In the spraying experiments con¬ 
ducted by the writers, approximately 
13,000 plants were used during the 
several seasons in which the work was 
done at Manhattan. (See fig. 2.) 
The yield of grain per plant always 
increases with the percentage of smut 
found in the plant. In other words, 
the effect of the fungicides has been 
to decrease not only the smut but also 
the yield. The figures on yield may 
be accepted as a measure of the general 
reduction in vegetative vigor due to 
injury done by spraying. It seems 
therefore, that an adequate interpre¬ 
tation of these data, which obviously 
give a distinct indication of smut 
control, must give due consideration 
to the host injury occasioned. Arthur 
and Stuart (2) noted some such injury 
in their experiments and, as in the 
work at Manhattan, were not successful 
in attaining complete control. Their 
conclusion, however, that true fungi¬ 
cidal control had been attained would 
seem hardly to be justified by the mere 
fact of reduction in infection per¬ 
centages. Plants which have been so 
definitely reduced in vegetative vigor 
would necessarily produce less meriste- 
matic tissue, a circumstance which 
involves a correspondingly lessened 
production of smutted tissues. 
In order to understand the spraying 
results at Manhattan, Kans., it seems 
sufficient to present only briefly the 
formulas of the sprays used. The 
Bordeaux mixture sprays were: 6-4-50, 
4r-5-50, 3-4-50, 1-1-50, and the lime- 
sulphur solutions were 1 park* of the 
concentrate to 30 or 40 parts of water. 
Formaldehyde solutions of the strength 
0.1 and 0.2 per cent were used, and 
during one season CuSo<, one part to 
100 of water, was tried. 
In support of the conclusion that 
true fungicidal control is doubtful, may 
be mentioned the fact that both conidia 
and chlamydospores will germinate on 
glass slides sprayed with certain 
strengths of Bordeaux mixture, copper 
sulphate, and lime-sulphur. Similar 
observations have also been made by 
Dandeno (5). The writers have made 
no effort to analyze the many compli¬ 
cations involved in comparing these 
laboratory germinations with results 
obtained from the use of these fungi¬ 
cides in the field. It is only desired to 
present here the observation corrobo¬ 
rating the conclusion that it is very 
questionable whether real fungicidal 
effect has been attained in any at¬ 
tempts to control corn smut by spray¬ 
ing. 
The efforts to prevent infection 
having yielded essentially negative 
results, it would appear desirable to 
note the points on which further re¬ 
search might yield results and indicate 
the lines of procedure for developing 
possible control measures. Since it has 
been shown that the smut fungus 
exists in an active virulent condition 
in the leaf axils of corn in the field, it 
appears possible that some way might 
be found for suppressing such viru¬ 
lence, even though the culture actually 
can not be killed without injury to the 
host. Piemeisel (16) has shown that 
virulence may be retained for some 
time in artificial culture. The exper¬ 
ience of the writer substantiates this, 
but since some cultures apparently lose 
the power to infect, it seems more perti¬ 
nent to the problem of control to dis¬ 
cover when and why virulence is lost. 
If the answer to this question discloses 
no feature which could be put to prac¬ 
tical use in controlling the disease, 
there still remains a possibility that 
methods of applying chemical dusts 
or even of other sprays may be devel¬ 
oped which will avoid injuring the 
plant. This must be accomplished 
before satisfactory observations of con¬ 
trol can be made, and probably will 
necessitate trials with other chemicals 
than the fungicides commonly used as 
liquid sprays. 
DATE OF PLANTING 
Studies have been made during sev¬ 
eral seasons on the effect of the date of 
