Bordeaux Mixture
Fungicides are mixtures of chemical compounds made
up for the purpose of controlling plant diseases caused by a class of
plant weeds known as fungi. There are three commonly well known and
used fungicides, Bordeaux mixture, commercial lime sulphur, and the
self-boiled lime-sulphur. The
Bordeaux mixture is the best all-around
fungicide known. It is a mixture of three pounds of copper sulphate
(blue vitriol or bluestone) with three or more pounds of fresh burned
stone lime in fifty gallons of water. The two compounds should be put
together as fruit growers say "with water between," that is each
should be diluted with the water separately before the two are mixed.
The best plan is to have stock mixtures of each in barrels, fifty
gallon cider or vinegar barrels making good receptacles for the
purpose. Place the bluestone in an old fertilizer or meal sack and
suspend it about midway in the barrel of water. In a few hours it will
all be dissolved and will remain in suspension for some length of time
very well. If say fifty pounds of the copper sulphate are dissolved in
fifty gallons of water, each gallon of water will contain one pound of
the bluestone, which makes a very convenient way to measure it. So
also fifty pounds of fresh burned stone lime should be placed in a
barrel--in this case in the bottom of the barrel rather than in a
sack--just covered with water and allowed to slake, more water being
added as required up to fifty gallons. If too much water is added to
the lime at the first it will be "drowned" and its slaking checked.
These two stock mixtures, each gallon containing one pound of the
copper sulphate or one pound of the lime, are then mixed together.
It is well to fill the tank about half full of water, then put in the
required amount of the copper sulphate, and after stirring well add
the lime milk. It is a good plan to add an excess of lime as it
minimizes the danger of burning and aids the mixture in sticking to
the leaves well. If one is sure that he has at least as much lime, or
an excess of lime, it will not be necessary to test the mixture, but
if he is not, a simple test may be made with ferro-cyanide of
potassium, obtained at a drug store. A few drops of this mixture will
disappear if the lime is equal or in excess of the copper sulphate,
that is, it will be neutralized, but if it is not, they will remain a
bright purplish red. Bordeaux mixture is used in strengths varying
from three to five pounds each of bluestone and lime in fifty gallons
of water, but the former is usually sufficient.
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Next: Lime-sulphur
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