The progressive farmer. [volume] (Winston, N.C.) 1886-1904, 1891-07-07

must be arrested and executed, like
the malefactors they are. By spray
ing an infected plant we destroy its
spores as they issue from the host
plant; by spraying a still healthy plant
we give it a protective covering of
powder, poisonous to the spores of
fungi, which kills the spores as they
aIight upon the leaves and branches.
Spraying is therefore always preven-
tive, never curative.
The fungicide most commonly en-
ploped in this country is the Bordeaux
mixture, which as commonly made
contains six pounds of copper sulphate
to each % gallons. To spray one acre
of grapevines once, takes about sc gal
Ions of this mixture and usually six
treatments are required for each sea-
son. This gives a total of about 400
gallons per acre, containing about 1O8
pounds of copper sulphate. All of this
copper eventually finds its way into
the soil. AS we have seen, copper
salts are deadly poison to all absorp-
tive plant tissues, and therefore to the
roots of cultivated plants. Is there
not danger then that the accumulation
of this sub stance in the soil of our
gardens and orchards, if persisted in
for a series of years, may eventually
affect the fertility of the soil? There
is very great danger. And let it be
understood that when once the soil is
sterilized by this poison, not all the
guanO on the coast of Peru can ever
restore it to its former state, or make
it fit to bear one blade Of grass
The possible danger Of using such
poisons has already occasiOned cOnsid
cradle alarm in Europe. 1t came up
for discussion at the last meeting of the
German association of naturalists. 1t
was shown that copper sulphate in the
soil soon becomes copper oxide, which
is practically insoluble and remains in
the upper stratum of the soil The
sulphuric acid in the copper sulphate
combines with the potash and lime in
the soil and with them forms more or
less soluble compounds which are
washed into the drains or s. far below
the reach of most plants as to be prac
ticaly lost. It's deleteriOus action is
therefore twOfOld: It destroys the
young roots Of plants and causes the
useful potash and lime in the soil to
leach away. When lime is added to
the copper before it is sprayed, the
baneful effect of the latter upon the
potash and lime in the soil is largely
prevented, but its evil effect upon the
growing plantroots still remains. The
hOrticulturist must therefore bear in
mind that the fungicides he uses are
by no means friends to be depended
on without limit. They are necessary
evils, to be used with caution and the
greatest economy. BY hygienic pre-
cautions the amount of copper salts
used can be greatly decreased.
The quantity of copper which sufffces
to make a liquid destructive to absorp-
tive plant tissues is surprisingly small.
1t was recently noticed at German
seed control stations, that distilled
water seemed to be poisonous to young
plantlets grown in the process of test
ing the vitality of seed. After much
xperimentation the trouble was found
to be caused by the almost infnitesi-
NAL quantity of copper dissolved by
the water in passing through q copper
still. From this fact we should judge
that the amount of copper used in the
Bordeaux mixture is much larger than
is necessary. In fact, European ex
periments- especially those at the St.
Michael Experiment Station in the
Tyrol-show that a very much weaker
mixture will often give as good results
At this station the Bordeaux mixture
was madewith copper sulphate varying
from two per cent. to one-fourth per
cent, that is, with from A pounds to
one-half pound of copper sulphate to
twenty-six and onehalf gallons of
water. The weakest form gave as
good results as the stOngest. as is
well known to grape-growers and
others who use the Bordeaux mixture,
it is usually all washed off by the first
rain. Since we have seen that the
presence of a mere trace, if it be well
diffused, is sufficient to protect the
foliage from infection, the safest way
would seem to be to use a weak sOlu
ton and put it on in the finest possible
spray, just enough to wet the foliage,
with repetition of the treatment as