Aug. 15,1925 
Soil Disinfection for Potato Wart 
351 
Toxicity of Mercuric Chloride Plus Sodium Chloride Solutions After 
Passing Through Soil 
The effect of passage through soil on the toxicity of the HgCl 2 + 
NaCl solution was tested with only a few tubes of heavily infected 
soil from Freeland, Pa. Sixteen tubes were prepared in the usual 
manner on January 26, 1922. Thirteen tubes were treated 1 + 1 
and 3 tubes were treated with water plus water to serve as checks. 
In eight days 3 of the 13 treated tubes were tested for mercury pene¬ 
tration. Positive tests were secured in each inch of soil in all three 
tubes from the surface to a depth of 9 inches. Twenty-six days 
after treatment the soil was removed from all tubes and used to 
inoculate tubers. Pots were partly filled with uninfected soil, a 
tuber laid on the sod, and 1 inch of sod removed from one of the 
tubes was scattered over the tuber and sod. The pot was then 
fill ed to the proper height with uninfected sod. At the end of three 
months the potato plants were examined for wart. 
As shown by Table XVII, the 90 pots inoculated with sod, from 
the surface to a depth of 9 inches, in the treated tubes remained free 
from wart infection. Of 29 pots inoculated with sod from treated 
tubes but from below the 9-inch depth to which the mercury had 
been shown to penetrate, 6 pots, or 21 per cent, showed wart. Of 
the 35 pots inoculated with sod from the check tubes 10 pots, or 29 
per cent, showed wart. A second series of tubes gave almost identical 
percentages of infection. Apparently the treatment of sod with 1 
per cent HgCl 2 + 5 per cent NaCl solution at the rate of gallon 
per square foot and fodowed by an equal amount of water is effective 
to the maximum depths of penetration in the Freeland sod. 
Table', XVII. — Effect of soil penetration on toxicity to the potato-wart organism of 
mercuric chloride plus sodium chloride solution as shown by infections of potato 
plants grown in pots inoculated with soil from different depths in treated tubes 
Depth from 
which in¬ 
oculation 
soil • was 
taken 
Inoculated 
with water- 
treated soil 
Inoculated 
with 1+1 * 
treated soil 
Depth from 
which in¬ 
oculation 
soil ° was 
taken 
Inoculated 
with water- 
treated soil 
Inoculated 
with 1+1 * 
treated soil 
Plants 
ex¬ 
amined 
Plants 
show¬ 
ing 
wart 
Plants 
ex¬ 
amined 
Plants 
show¬ 
ing 
wart 
Plants 
ex¬ 
amined 
Plants 
show¬ 
ing 
wart 
Plants 
ex¬ 
amined 
Plants 
show¬ 
ing 
wart 
Num¬ 
Num¬ 
Num¬ 
Num¬ 
Num¬ 
Num¬ 
Num¬ 
Num¬ 
Inches 
ber 
ber 
ber 
ber 
Inches 
ber 
ber 
ber 
ber 
Otol 
3 
1 
10 
0 
6 to 7 
3 
1 
10 
0 
1 to 2 
3 
1 
10 
0 
7 to 8 ' 
3 
0 
10 
0 
2 to 3 
3 
1 
10 
0 
8 to 9 
3 
2 
10 
0 
3 to 4 
3 
0 
10 
0 
9 to 10 
3 
1 
10 
1 
4 to 5 
3 
1 
10 
0 
10 to 11 
3 
1 
10 
4 
5 to 6 
3 
0 
10 
0 
11 to 12 
2 
1 
9 
1 
« Wart-infected soil from Freeland, Pa., containing 12.8 per cent moisture. 
b For explanation of symbol, see p. 332 and footnote of Table VII, page 339. 
Relation of Soil Penetration of Water Solutions to the Amount Applied 
. i 
With the glass soil tubes used the penetration of water could be 
readily determined at any time in most soils, particularly if dry, by 
