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"' AnOCU'MEp s nt
awali Agricultural Experiment Staton,-
-\ U.S. DEPOSITORY
I E. V. WILCOX, Special Agent in Charge
:..... PRESS BULLETIN NO. 25
;Cfarbon Bisulphid for Killing
By E. V. WILCOX,
Special Agent in Charge, Hawaii Agricultural Experi:
Station, United States Department of Agriculture.
In the perpetual conflict with weeds it becomes necessary
to make use of every weapon which shows efficiency in destroy-
ing them. The conditions under which different crops are
.raised indicate different methods as best adapted to the vari-
ous conditions of each case. During the past year a number
of experiments have been made with carbon bisulphid in
studying its effects upon various herbaceous and shrubby
weeds. In these experiments, the amount of carbon bisulphid
used varied according to the size of the plant to be destroyed.
On small-stemmed plants like Crotalaria, about a teaspoonful
of commercial bisulphid was poured down the stem, from about
six inches above the ground. The amount was increased, for
larger plants, up to two tablespoonfuls for guava bushes three
or four inches in diameter. The plants upon which most of
the tests were made were lantana, guava, prickly-pear, Stachy-
tarpheta dicotoma (one of the plants known by the native name
,Oi), and Crotalaria incana. In all cases, as just indicated, the
carbon bisulphid was poured on the stem at a point about six
inches above the surface of the ground. On most plants carbon
bisulphid shows no effect until after the lapse of a considerable
period; on large guavas sometimes two or three months. The
effect of pouring carbon bisulphid on Crotalaria was to cause l
the death of the plant, root and branches, within four to ten .
days. The plants remain green, and apparently normal, until ,-,ii
shortly before death, when the leaves suddenly turn yellow
and shrivel up. If the plants are then carefully removed from
the soil it is found that all of the root-system is dead and the
inner tissues of the roots and lower part of the stem are brown,
.of otherwise discolored.
Lantana bushes, about two inches in diameter, died within
seventeen to thirty-two days after the application of carbon
'bisulphid. About the same length of time was required for
.the destruction of Oi. Young prickly-pear plants, about two
feet in height, were found to be exceedingly sensitive to car-
A'' bon bisulphid. In some cases, the plants fell over on the ground
within twenty-four hours after being moistened with the
liquid; and in other cases, were dead within two days.
With guava, the effects of carbon bisulphid were not mani-
fested for a much longer period, in some cases even not for
two or three months. Finally, however, in all but two cases
the leaves turned yellow, withered up, and the plant died. The
dead and dying trees were dug out and the roots examined.
In every case the roots were found to be dead to the tip and
their whole tissue discolored. In one case, the guava tree was
over six inches in diameter at the base.
Apparently, the effect of carbon bisulphid, when applied
directly to the stems of plants, is due to artificial freezing. As
is well known, the liquid volatilizes almost instantly and cools
the surface so suddenly that the living bark is destroyed. It
was found to be a simple matter to produce ice at noon on hot
days on the surface of guavas and other plants by.slowly drip-
ping carbon bisulphid along the trunk. The death of large
guavas from an application of a small quantity of carbon
bisulphid to the base of the trunk, a few inches above the
ground, can hardly be attributed entirely to the freezing effect.
It seems also to exercise a poisonous action, otherwise it would
be difficult to explain the complete destruction of the roots to
their tips, in some instances, six or eight feet from the point
where the carbon bisulphid was applied. It was found, for
example, that guava bushes would live for five to seven months.
after the bark and cambium had been entirely removed from
the surface of the ground up to a height of two feet. More-
over, the destruction of the bark at the base of the trunk by
concentrated sulphuric acid was not sufficient to cause the
death of the guava bush for about six months. Apparently,
therefore, carbon bisulphid causes the death of plants by its
freezing effect and also by a poisonous action.
The use of carbon bisulphid for destroying underground
insects is a familiar practice. It may be interesting, therefore,
to inquire what effect, if any, the extensive use of carbon bisul-
phid may have upon the soil and its adaptability to cultivation.
It is well known, for example, that the application of carbon
bisulphid to the soil around fruit trees and other plants has
no injurious effect upon the plants; in fact, 1Hiltner and
Stormer have shown that carbon bisulphid reduces denitrifica-
tion and the fixation of nitrogen. Similarly, 2Heinze demon-
strated that carbon bisulphid promotes the activity of nitrogen-
fixing organisms. In experiments carried on by Nobbe, the
yield of peas, and various other crops, was increased as a result
of the application of carbon bisulphid and the plants absorbed
more ash and nitrogen. SHenry found that when 400 cc. of
carbon bisulphid per square meter was injected into the soil
about locust trees, beneficial effects upon the growth of the
trees were observed for several years. On the other hand,
heavy fumigation with carbon bisulphid has frequently proved
injurious or fatal to young fruit trees. In a series of experi-
ments by 4Oberlin, carried on for eighteen years, in treating
grape Phylloxera, it was found that carbon bisulphid had a
remarkable effect in increasing the yield of grapes. When
other crops were rotated with grapes, for example, legumes,
1. L. Hiltner and K. Stormer, Arb. K. Gesundheitsamte, Biol. Abt. 3
(1903) pp. 443-545.
2. B. Heinze, Centbl. Bakt., etc., 2 Abt. 16 (1906) pp. 329-358.
3. E. Henry, Bul. Soc. Sci. Nancy, 3 Ser. 2 (1901) pp. 27-33.
4. C. Oberlin, Jour. Agr. Prat. 59 (1895) pp. 459-464, 499-503, 535-540.
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sugar-hbets, and cereals, "a considerably ein
also noted in these plants. In a few. intatte%,
soil made "sick" by continuous ciiture of these'
restored to productiveness by the use of caThon b`
Apparently the only previous experiments.
bisulphid, as a weed-destroyer, were crie' rd.o bit
Arkansas in destroying sassafras sprouts, andpc r I
in Maryland; also on sassafras. In both -of thesloe
chemical was found to produce. the death of oh p
one month. .. *
In using carbon bisulpiud it should alvays'e
that the fumes, if inhaled continuously, may produce
effects upon the workmen, and also that the material s
inflammable and should be protected from accidental
The effects of the fumes upon workmen, include head
ziness, hysterical excitement, and, finally, a rather2.ei
weakness, a feeble pulse and other symptoms of pr j
If it is used, therefore, in the eradication of weeds, theep
should be borne in mind in order to protect the wor
It is obvious that carbon bisulphid, although -.an :e
means of destroying certain weeds, cannot be used iei
Sally in all localities. There are many steep slopes .c.
with guavas, in which it would be a very difficult '
operate with this chemical. It is always necessary.
workmen to keep to the windward, in order to a..l.
fumes, and in some localities the difficulty of transporti~ntoft
tainers would render the method entirely impracticable:
the other hand, the use of carbon bisulphid in the destructiOle
of such plants as the guava has the advantage that yQo4$ !
sprouts do not come up from the roots. The necessity of gr :i
bing out all of the roots is thus obviated. Under such cire~cu-
:stances, it would merely be necessary to allow the-guaY"vOa
:stand until they are dead, after which the trunk and la'
roots would be removed, as is necessary in any ease in eleant
the land. -
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