Feb. 15,1925 Root Rot of Peas Caused by Aphanomyces Euteiches 315 
Table II.— The pathogenicity of Aphanomyces euteiches to Alaska peas at the 
series of soil temperatures and in soil at the three conditions of soil moisture in¬ 
dicated (series of November 18, 1928 ) 
Temperature in°C. 
12° 
18° 
24° 
0 
o 
CO 
Per cent moisture-holding 
capacity of soil. 
35 
60 
80 
35 
60 
80 
35 
60 
80 
35 
60 
80 
Number of plants Dec. I... 
25 
27 
25 
27 
26 
26 
25 
25 
24 
28 
26 
27 
Number of plants wilting 
and removed at date in- 
dicated: 
Dp.n 1 
1 
2 
3 
Dec. 2 
2 
4 
2 
Dec. 6 _ 
2 
1 
7 
7 
6 
Dec. 8.. 
_ __| . 
1 
2 
3 
1 
7 
2 
Dec. 13 
1 
2 
8 
5 
4 
4 
2 
Dec. 17 
__ 
1 . .. 
3 
2 
1 
5 
2 
2 
1 
i 
Total number of 
dead plants. 
... 
3 
4 
5 
15 
14 
18 
(°) 
20 
16 
Number of plants with de- 
cayed stem bases Dec. 18__ 
3 
9 
3 
10 
19 
11 
10 
4 
( b ) 
1 
3 
8 
Total number of plants in- 
1 
fp.ntfid . . 
3 
9 
3 
13 
23 
16 
25 
18 
1 
23 
24 
Healthy plants, Dec. 18_ 
25 
21 
25 
15 
5 
8 
0 
5 
( b ) 
12 
4 
1 
* One of the two cans at this temperature and moisture developed a leak and was discarded. 
b Data missing. 
Table III.— The pathogenicity of Aphanomyces euteiches to Alaska peas at the 
series of soil temperatures and at the three conditions of soil moisture indicated 
(series of December 19, 1922) 
Temperature in 0 C. 
10° 
12 ° 
15° 
1 
j 
18° 
21° 
24° 
Per cent moisture-hold¬ 
ing capacity of soil-.-. 
36 
60 
80 
36 
60 
80 
36 
60 
80 
36 
60 
80 
36 
60 
80 
36 
60 
80 
Number of plants Jan. 5. 
27 
36 
32 
34 
34 
28 
38 
24 
32 
39 
31 
28 
Number of plants wilting 
! 
and removed at date 
indicated: 
•Tan. 2 
1 
1 
_ 
1 
3 
.Tan. 6 
2 
1 
.T an 9 
1 
5 
4 
3 
4 
1 
13 
.Tan. 12 
! 
2 
1 
1 
6 
3 
Jan. 19. . . 
3 
"T 
4 
---- 
1 
3 
7 
~~2 
4 
Total number of 
1 
! 
plants killed_ 
1 
6 
5 
1 
11 
— 
7 
8 
17 
4 
23 
Number of plants dis¬ 
t 
i 
= 
eased Jan. 30 . 
1 
1 
2 
0 
! 2 
17 
8 
10 
22 
19 
6 
10 
5 
17 
12 
7 
5 
Total number of 
i 
! 
plants infected .. 
1 
1 
2 
0 
1 2 
17 
8 
16 
27 
20 
17 
10 
12 
25 
29 
11 
28 
Healthy plants Jan. 30. . 
29 
20 
30 
32 
! 19 
1 
14 
25 
16 
6 
13 
10 
24 
13 
8 
7 
j 17 
0 
The soil from this experiment was 
used for a third series in the tempera¬ 
ture tanks, in which the method was 
modified for the purpose of learning 
whether infection occurring later in 
the development of the plant would 
produce less wilting than early infec¬ 
tion. The soil was dried until it con¬ 
tained 30 per cent of its moisture¬ 
holding capacity, mixed thoroughly, 
and placed in cans. Peas were planted 
on February 10, and the entire series 
was kept at a soil temperature of 12° 
C. until February 24, when most of 
the plants had emerged, though not all 
had assumed an erect position. Tem¬ 
perature was adjusted to 15°, 18°, 21°, 
and 27°, and water was added to bring 
the soil up to 60 per cent of its moisture¬ 
holding capacity. New inoculation 
of these plants was then made by 
pouring a ' suspension of zoospores 
around the bases of all plants, and the 
surface soil was kept moist for the 
three following days. In five days a 
few plants at 27° showed infection at 
the surface of the soil, from which 
they died later; but there was so little 
infection at the lower temperatures 
that the results of this series are not 
