30 
BULLETIN 1451, U. S. DEPARTMENT OE AGBICULTUEE 
It is evident that this method of application is inefficient. The 
quantity of the material used for a bush unquestionably was suf- 
ficient to cause the death of the bush, if the hydrocyanic-acid gas had 
been liberated and allowed to act on the roots. Death did not result 
in every case. This deficiency may have been due to some peculiar- 
ity of the soil or of root conditions of the particular bushes that pre- 
vented the gas from reaching all the roots, or to the failure of hydro- 
cyanic-acid gas to remain free in the soil. 
CARBON BISULPHIDE 
Carbon bisulphide (CS 2 ) at ordinary temperatures is a heavy liquid 
which vaporizes readily. The vapor is heavier than air and readily 
penetrates soil that is not too wet. It has been used to some extent 
as a herbicide, as for instance by Wilcox (18) , but it has had a greater 
use as an insecticide. Hinds (6) states that it kills insects by dis- 
solving fats, coagulating proteins, and preventing the assimilation 
of oxygen. 
In the greenhouse 2.6 grams of carbon bisulphide applied to the 
surface of the soil in 8-inch pots of small barberries -caused the death 
of the plants in eight days. This was considered equivalent to a 
dose of about one-half pound to the bush in the field. As the ma- 
terial could be purchased for about 6.5 cents a pound, it was tried 
in the field. In Table 9 the results of the field tests are given. 
Table 9. — Summary of treatments of individual, marked barberr 
carton bisulphide 
tushes with 
Date of 
treat- 
ment 
Date of 
final ob- 
servation 
Quan- 
tity of 
chemi- 
cal per 
bush 
Method of application 
Bushes cut 
off or left 
standing 
Location of 
area 
Bushes 
treated 
Bushes 
killed 
Per- 
centage 
killed 
1922 
May 9 
Do— 
Do— - 
Do- 
July 10 
May 9 
July 10 
Oct. 16 
1923 
July 3 
...do.... 
—do 
—do 
...do 
...do..-. 
...do.-.. 
Pints 
1.00 
1.00 
2.00 
2.00 
1.00 
1.00 
1.00 
1.75 
Poured in four holes, 8 
inches deep, around 
crown. 
do 
do 
do 
In circle of 1-foot radius 
around crown. 
Drench in and around 
crown. 
do.. 
do 
Standing.. 
Cut off 
Standing.. 
Cut off- 
Standing.. 
—do 
Cut off- 
Standing. . 
Gurnee, Dl.. 
do 
do 
do-.— 
do 
do 
do 
do 
20 
20 
20 
20 
20 
5 
20 
90 
17 
15 
16 
13 
!8 
4 
20 
77 
85 
75 
80 
65 
90 
80 
100 
86 
Total. 
215 
180 
84 
It appears from these results that 1 pint is as efficient in killing 
barberries as 2 pints, also that carbon bisulphide is equally effective 
when poured on the surface of the soil and when applied in holes 
around the crown. Though a large percentage of the bushes treated 
were killed, in only one case were all the bushes of a treatment 
killed. These differences no doubt were due to the type and physical 
condit'on of the soil around individual bushes, as well as to varia- 
tions of the root system. In light, dry soil carbon bisulphide dif- 
fuses rapidly, but in heavy, wet soil the diffusion is slow. A satis- 
