Year: 1875

POISONS IN AGRICULTURE.


A Paper Read Before the American Health


Association by r. C. Kedzie.


In this contest with insect foes the
farmer often finds poisons the most
ready means of defense, but great care
should be exercised in the use OF
such agents. Not only the immediate
benefits, but also the remote and contin-
gent consequences demand attention. A
safe insect poison should combine the
following properties: First, it should.
in small quantity, effectually destroy
the insect second, it should be easy to
apply; third, It mutt not injure the crop
in any way or endanger the health of
the consumer of the crop; fourth, it
must not injure any succeeding crop ;
fifth, it must not injure the health of
the person who applies it: sixth, it
should be easily distinguished from
other substances in use on the farm and
in the household. No substance has yet
been found which combines all these
qualities. Mr.. Kedzie's paper WAS con-


fined to the consideration of the arseni-
cal poisons, viz: "white arsenic, "
arsenate of soda, and paris green, and
after pointing out the dangers from
their use and the influence of arsenic on
plant-ife, citing the experiments Of
Prof. Edmund Davy, and counter-e1-
periments of Ogston, Of Daubeny and
Brodie, also the experiments OF Nc
Murtrie, of the department of agricul-
ture, he considered the questions Will
paris green poison plantsi Will it re-
appear in those parts of plants used for
fooda Used in large quantity it may
kill the potato vines, but does not reap
pear in the potato tuber. Such potatoes
have been used for years in large guam
titles, but no case is known of poison
ing by their use. Direct inquiries made
by the Michigan State board OF health
resulted in answers from more than 1000
clerks of local boards of health, and in
1873 only five clerks reported cases OF
poisoning by the use of paris green.
By further examination it was found that
in the cases reported no one was pois-
oned by eating the potato, but only by
careless handling of the paris green.
When paris green is applied to wheat
during it's period of growth, or is present
in the soil on which wheat is grown
from having been applied to previous
crop, the arsenic did not appear in the
grain, and thus injure or destroy its
value as food, nor was it found in the
straw. Experiments with cabbage raised
On soil dressed last year with paris green
to destroy potato beetle showed no
arsenic in the cabbage. To the ques-
tions: What becomes Of paris green in
the soili Why does it not reappear in
vegetables, nor poison our wells and
fountainsl The reply that it is insolu-
BILE in pure water is not enough, for it
is sensibly soluble in the natural agri-
cultural solvents. The paper, in dis
cussing these questions, cites many e1-
periments to show the action of the soil
on chemical substances, and particularly
on paris green, which established that
paris green after three months con-
tact with the soil, does not exist as aceto-
arsenite of copper; that the material
had not washed out of the soil, and that
the arsenic comported itself, so far as
solubility is concerned, as it would if it
existed in the form OF basic arsenite OF
iron. The conclusions drawn are that
paris green being deadly poison should
be handled with extreme care, as inhala-
tion of the dust by contact of the ma
terial with sores and raw surfaces, and
even by contact with moist and perspir-
ing surfaces, it may produce dangerous
effects that while classed as an insolu-
BILE substance, paris green becomes
soluble to q sensible degree by the &C
ton of what may be called the natural
agricultural solvents, of which carbonic
acid and the solvent action of the minute
roots of plants may be regarded as the
most active that solutions OF arsenious
acid and of arsenites tend to pass into
an insoluble condition in the soil, In
which arsenic is insoluble by the natural
agricultural solvents; that while other
agents may assist i'll fixing arsenious
acid in the soil, the hydrated oxide of
iron is probably the most potent factor
in producing this insoluble condition !;
that enough of this oxide is present in
all fertile soils to render inert a COM
paratively large amount of arsenic, and
that it is to this agent that we probably
owe our safety when paris green is ap-
piled to the soil. When paris green is
applied to tho soil in such quantity that
the hydrated oxide of iron present in
such soil is not sufficient to speedy
change it to the inert condition, we
should expect this agent to injure the
health, or even destroy the life of the
plant. The limit of safety would natur-
ally vary with varying composition of
soils. Mr.. McMurtrie places the limit
in one instance at nine hundred pounds
to the acre, quantity vastly in excess
of any requirements as an insect poison.
Finally, the power of the soil to remove
from solution and hold in an insoluble
form arsenious acid and arsenites, will
protect the water supply from deadly
contamination by this agent, unless the
poison is used in excess of any require
ments as an insect destroyer.


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