Nov. 3, 1923 
Helminthosporium Disease of Wheat 
209 
rium disease, even in connection with the alternating soil temperature 
experiment cited above, but doubtless the relation of such high tem¬ 
perature to the previous and following temperatures to which the plant 
is submitted has some bearing on this point. 
soil, moisture: studies 
Three greenhouse experiments have been conducted in connection 
with the soil-moisture studies. In the case of experiments 1 and 2 all 
of the plants were grown at the same greenhouse temperature (15 0 to 
25 0 C.) during the experiments. In the case of experiment 3, the 
moisture study was combined with the fifth soil-temperature experiment 
with Harvest Queen wheat. 
EXPERIMENTAL METHODS 
The methods used in these experiments were the same as those employed 
in the soil-temperature experiments. In all cases disinfected seed was 
inoculated with a water suspension of conidia just before sowing. Seeding 
was not done until the soil moistures had been carefully adjusted on a 
basis of the usual soil-moisture tests. 
During the period of experiment the pots were weighed daily and 
moisture adjustments made as needed. No difficulty was experienced 
in adjusting the middle and higher moistures, but there was some diffi¬ 
culty in adjusting the lower ones on account of uneven moisture dis¬ 
tribution. This adjustment was facilitated, however, by applying water 
often around the edge of the soil next to the pot wall and by keeping 
a light dust mulch on the surface. 
In experiments 1 and 2, metal pots 5 inches in diameter and 9.5 inches 
deep were used; in experiment 3, metal pots 8 inches in diameter and 
9.5 inches deep were used. 
Table VI. —Results of experiments on the relation of soil moisture to the infection of 
Marquis and Harvest Queen wheat seedlings by Helminthosporium sativum when 
artificially inoculated seed was sown in a sandy loam soil having a moisture-holding 
capacity of 36 per cent, at Madison, Wis., in IQ22 
Experiment i. 
Experiment 2. 
Marquis seed sown, culture 51a used. 
Harvest Queen seed sown, culture 
Experiment started Jan. 5, 1922; 
392 used. Experiment started 
ended Jan. 30, 1922. 
Feb. 28, 1922; ended April 12, 1922. 
Percentage 
Percentage 
of moisture¬ 
Number 
Infection 
of moisture¬ 
Number 
Infection 
holding 
of plants. 
rating. 
holding 
of plants. 
rating. 
capacity. 
capacity. 
22. 2 
O 
O 
27. 7 
80 
0.8 
33-3 
168 
22. 6 
33-3 
80 
13.0 
44-4 
173 
29. 1 
44.4 
80 
18.3 
55-5 
163 
5 °* 4 
55-5 
75 
26. 5 
66.6 
151 
64.3 
66.6 
69 
30 - 5 
77 - 7 
126 
48. 2 
77 - 7 
13 
31. 2 
