ERADICATING THE COMMON BARBERRY 
29 
When the bushes were cut down before being treated, the stumps 
sprouted in nearly every case. The sprouts grew well for several 
months before there was noticeable injury, and not until the second 
year was it evident that many of them would not survive. 
CALCIUM CARBIDE 
Calcium carbide (CaC 2 ), when moistened, forms acetylene gas 
(C 2 H 2 ), which frequently is used for illuminating purposes and for 
welding or cutting metal. This gas has been reported to be very 
toxic to plants. 
On October 31, 1921, 36 mid-sized barberries growing in the field 
at Gurnee, 111., were treated with calcium carbide at the rate of 
about 2% pounds to the bush. Several holes about 10 inches deep 
were made with a crowbar around the base of each bush, and the 
carbide was inserted ; then . the holes were filled with earth and 
tamped. Twenty-one of the bushes were left standing and 15 were 
cut down before treating. None were dead at the time of the final 
observation, 21 months later. 
On April 28, 1922, 40 bushes in the same locality were treated in 
the same manner but with a dose of only 2% pounds to the bush. 
Half of these bushes were cut down and the other half left standing. 
Thirteen months later 2 of the 20 that had been cut down were dead, 
but all the others were living and apparently uninjured. 
Evidently acetylene gas is not very toxic to common barberries or 
else the method of application used was not such as to permit the gas 
to reach the living tissues of the plants. No further experiments 
were made with this substance. 
CALCIUM CYANIDE 
The commercial calcium cyanide used was obtained from a manu- 
facturer and was said to contain about 45 per cent of calcium 
cyanide (Ca(CN) 2 ), 30 per cent of sodium chloride, 12 per cent of 
lime, and a small proportion of graphite and other inert ingredients. 
This chemical has been reported as a very effective herbicide when 
sprinkled on the surface of moist ground and covered with paper, 
straw, or similar materials, in order to retain the hydrocyanic gas 
evolved. As such a procedure was scarcely feasible with large num- 
bers of barberry bushes, the cyanide was placed in holes about 6 
inches deep and close about the crown of the bush. (Table 8.) 
Table 8. 
-Summary of treatments of individual, marked barberry bushes with 
calcium cyanide 
Date of 
treat- 
ment 
Date of 
final 
observa- 
tion 
Quan- 
tity of 
chemi- 
cal per 
bush 
Method of application 
Bushes 
cut off 
or left 
standing 
Location 
of area 
Bushes 
treated 
Bushes 
killed 
Per- 
cent- 
age 
killed 
1923 
Aug. 10 
Do.... 
Sept. 10 
. 1924 
July 14 
—do 
—do 
— do.— 
Pounds 
0.25 
.25 
.75 
.75 
In holes about crown... 
— "do— — — — — — 
Standing. . 
Cutoff- 
Standing.. 
Cutoff.... 
Gurnee, 111.. 
do 
do 
do 
5 
5 
5 
5 
1 

4 

20 

80 

Total . 
20 
5 
25 

