434 
Journal of Agricultural Research 
Vol. XXV, No. II 
From the series of experiments Jones drew the following “tentative” 
conclusions: 
1. The use of steam-sterilized soil inoculated with cultures of Rhizoctonia was found 
to exaggerate very greatly the amount of injury which the fungus causes to appear. 
2. Rhizoctonia appears to do the greatest amount of injury to peas when the soil 
temperatures lie between 12 0 and 27 0 C. with a maximum amount or injury near 18 0 C. 
3. Within the limits tried neither high nor low temperatures completely inhibited 
injury from Rhizoctonia. 
4. Lesions produced by Rhizoctonia upon peas appear to be Characteristic, resem¬ 
bling those upon potatoes. 
5. It is frequently very difficult to reisolate Rhizoctonia from peas because of the 
presence of rapidly growing secondary invaders. 
6. In a single comparison of the pathogenicity of a strain of Rhizoctonia from peas 
and one from potatoes no difference was observed in the nature or the intensity of the 
injury done. 
7. Injury by Rhizoctonia to peas may be classified as follows: 
A. Destruction of the entire embryo of the germinating seed. 
B. Destruction of the primary shoot which may later be replaced by one or more 
secondary shoots. 
C. Production of lesions of greater or less intensity upon the stem below the surface 
of the ground. 
D. The early destruction of the cotyledons, thus depriving the young plant of its 
stored food. 
In the experiments on the pea conducted by the author three successive 
crops were grown in the “tanks” at soil temperatures varying from 9 0 
to 29 0 C. 
Experiment i.—I n this experiment peas were grown at the various 
temperatures in unsterilized pasture soil inoculated with Corticium vagum 6 
five days previous to planting. One can in each temperature tank was 
used for growing the Crop in the inoculated soil. A similar series with 
uninoculated soil was arranged as a control. Ten seeds were planted in 
each can of the two series, and 2 days later the tanks were adjusted to 
their various temperatures. The results obtained from the inoculated 
soil 19 days after planting are recorded in Table II. All control plants 
were found to be free from lesions. 
Table 11 .— Effect of growing peas at various temperatures in soil inoculated with Corticium 
vagum {Experiment 1) 
Temperature at depth 
of z inch. 
Number 
of seeds 
planted. 
Number 
of plants 
grown 
in unin- 
oculated 
soil. 
°C. 
0.2. 
IO 
0 
II.7. 
10 
y 
10 
xe.o. 
10 
10 
18.0. 
10 
0 
20.8. 
10 
y 
10 
22.< . 
10 
10 
26.6. 
10 
10 
10 
10 
y w . • 
Hants grown in inoculated soil. 
Total 
Number 
Number 
Num¬ 
ber 
cut 
off. 
Number 
Percent¬ 
Inten¬ 
sity of 
injury 
(points). 
num¬ 
ber. 
slightly 
injured. 
severely 
injured. 
unin¬ 
jured. 
age in¬ 
jured. 
7 
1 
6 
14. 2 
14. 2 
8 
4 
1 
3 
62.5 
75 -° 
9 
4 
I 
I 
3 
66. 2 
100.0 
8 
3 
3 
I 
1 
« 7 -S 
150.0 
10 
1 
2 
I 
6 
4a O 
80.0 
10 
1 
2 
7 
30.0 
50.0 
10 
IO 
* 
10 
10 
The results are especially interesting in showing the* inhibiting effect of 
the high and low temperatures on the pathogenic action of the fungus. 
No damage occurred to the plants at 26° and 29 0 C., and plants at 9 0 
6 This particular strain of Corticium vagurtt was provided by t)r. P. R. Jones, who had previously isolated 
it from diseased peas obtained in Wisconsin. The soil in the cans in Experiments x ahtf 2 Washiocnlated 
with small quantities of soil previously inoculated for this purpose with this specific organism. 
