Nov. 3, 1923 
Helminthosporium Disease of Wheat 
211 
Owing to the limited data available at this time, it is not possible to 
analyze the results of experiment 3 with complete satisfaction. However, 
the present evidence seems to in¬ 
dicate that soil temperature may 
be a more influential factor than 
soil moisture in connection with 
the development of the phases of 
the Helminthosporium disease 
under discussion. 
Fig. 4. —Graph showing the amount of Helmintho¬ 
sporium infection on the subterranean parts of Har¬ 
vest Queen wheat seedlings grown at different soil 
moistures when the soil temperatures were varied 
simultaneously. Note the rather consistent influence 
of temperature on the shifting of the moisture op¬ 
tima. Tabular results are given in Table VII. 
FIELD EXPERIMENTS 
All of the field studies have 
been made with soil naturally in¬ 
fested with Helminthosporium 
sativum. The plots were located 
on uniform gumbo soil in the 
American Bottoms of the Missis¬ 
sippi River near Granite City, 
Ill., just across from St. Louis, Mo. 
In order to get some idea of the 
influence of temperature on the 
Helminthosporium disease, two 
series of sowings of winter wheat 
were made at intervals during 
the autumns of 1920 and 1921. 
Each sowing consisted of a 
plot the width of an ordinary grain drill (54 inches) sown across the 
infested land. In 1920 these plots were 2 rods long and in 1921 they were 
5 rods long. In 1920 
Early May and Harvest 
Queen varieties were 
used and in 1921 Turkey 
and Harvest Queen were 
used. The dates of sow¬ 
ing are given in Tables 
VIII and IX. 
Owing to the distance 
of the field plots from 
the laboratory at Madi¬ 
son, Wis., and to diffi¬ 
culties in connection 
with getting some one 
to obtain accurate soil 
temperature and mois¬ 
ture records, it has been 
necessary to take the 
air temperature and 
precipitation data from 
the reports of the United 
States Weather Bureau 
at St. Louis, Mo. While 
these records do not represent the exact temperature and moisture 
conditions on the experimental plots, they approximate the general 
60376—23 - 2 
SO/L TEMPERATURES // V DEGREES CENT/GRAPE 
Fig. 5. —Graph showing the amount of Helminthosporium infection 
on the subterranean parts of Harvest Queen wheat seedlings grown 
at different soil temperatures and soil moistures. Same data as 
shown in figure 4, but plotted against soil temperatures instead 
of soil moistures. Note that varying the soil moisture did not 
cause the temperature optimum to shift in any case. Tabular 
results are given in Table VII. 
