Agricultural Uses
Bordeaux mixture is a copper fungicide invented by
Millardet of France in 1882. It is a mixture of copper
sulphate and lime (either quick lime or hydrated lime),
and is available commercially.
Bordeaux mixture is used for the control of numerous
plant diseases such as downy and powdery mildews of
grapes, scab or fire blight of apple, early and late blight of
potato and various leaf spot diseases.
Besides its fungicidal nature, Bordeaux mixture is
also used to control bacterial diseases like citrus canker,
caused by Xunrhomnus cirri. Bordeux mixture is most
effective when used fresh. When stored, it loses its
fungicidal property. However, the stability of the
mixture can be increased by adding sugar or jaggery at a
rate of 0.1 g/liter of water.
A range of formulations has been tried for the
preparation of Bordeaux mixture. Of these, the one used
often is 4-4-50, representing the respective percentage of
copper sulphate, lime and water. For preparing this
mixture, solutions of copper sulphate and lime are
prepared separately with sufficient quantities of water.
They are then simultaneously added to a third container
and the mixture is agitated vigorously. The containers
should preferably be wooden or earthen or of materials
that do not react with copper sulphate.
The advantages of using Bordeaux mixture are that it
(a) is cost effective, (b) has natural adhesiveness or
tenacity, (c) controls a wide variety of diseases, and (d) is
safe to handle. The disadvantages include its (a)
phytotoxicity on crops, especially on fruits like apple and
peach, (b) corrosive action on metallic containers or
equipment, and (c) tendency to delay ripening of the
fruit.
