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Bordeaux mixture
Home Bordeaux Mixture

Bordeaux mixture is a mixture of copper sulphate and slaked lime used as a fungicide. It is used in vineyards, fruit farms and gardens to prevent infestation of downy mildew, powdery mildew and other fungi.

In the year 1761, Schulthez first used copper sulphate for the seed treatment of wheat diseases. Later on Prevost termed copper as fungicide. The mixture of copper sulphate and lime was named as “Bouillie Bordelaise” (Bordeaux mixture).

Bordeaux mixture is generally accepted even in organic cultivation. It is easy to prepare and can be locally prepared by farmers themselves.

Preparation of
1% Bordeaux mixture

Materials required

1. Copper Sulphate – one kg
2. Lime – One kg
3. Water – 100 litres

Methodology

One kg of copper sulphate powder is dissolved in 50 litres of water. Similarly, 1 kg of lime is powdered and dissolved in another 50 litres of water. Then copper sulphate solution is slowly added to lime solution with constant stirring or alternatively, both the solutions may be poured simultaneously to a third container and mixed well.
Preparation of 0.5% Bordeaux mixture is same as above but reducing the copper sulphate and lime half of the amount but keeping water same as 1% mixture preparation. In general, 1% Bordeaux mixture is applied to hardy plant parts such as roots, stem and 0.5% of mixture is applied on leaf/foliage.

Tests to determine pH of the prepared
Bordeaux mixture

The ratio of copper sulphate to lime solution determines the pH of the mixture. The mixture prepared in the above said ratio gives neutral or alkaline mixture. If the quality of the used materials is inferior, the mixture may become acidic. If the mixture is acidic, it contains free copper which is highly phytotoxic resulting in scorching of the plants. Therefore, it is highly essential to test the presence of free copper in the mixture before applied.

There are several methods to test the neutrality of the mixture, which are indicated below:
  1. Field Test : Dip a well-polished knife or a sickle in the mixture for few minutes. If reddish deposit appears on the knife/sickle, it indicates the acidic nature of the mixture.
  2. Litmus paper test : The colour of blue litmus paper must not change when dipped in the mixture.
  3. PH paper test : If the paper is dipped in the mixture, it should show neutral ph.
  4. Chemical test : Add a few drops of the mixture into a test tube containing 5 ml of 10% potassium ferrocyanide. If red precipitate appears, it indicates the acidic nature of the mixture. If the prepared mixture is in the acidic range, it can be brought to neutral or near alkaline condition by adding some more lime solution into the mixture.

Precautions

The following precautions are needed during preparation and application of Bordeaux mixture.
  • The solution should be prepared in earthen or wooden or plastic vessels. Avoid using metal containers for the preparation, as it is corrosive to metallic vessels.
  • Always copper sulphate solution should be added to the lime solution, reverse the addition leads to precipitation of copper and resulted suspension is least toxic.

Advantages of Bordeaux mixture

  • Very easy and can prepared by farmers themselves.
  • Can act as fungicide, bactericide and algaecide.
  • Applicable to plant diseases such as foot rot, stem rot, leaf spot, leaf blight, anthracnose, canker, damping off, black spot, downy mildew, late and early blight etc.
  • It is less toxic to human as compared to other commercial fungicides.

Bordeaux paste

Bordeaux Paste consists of same constituents as that of Bordeaux mixture, but it is in the form of a paste as the quantity of water used is too little. It is nothing but 10 per cent Bordeaux mixture and is prepared by mixing 1 kg of copper sulphate and 1 kg of lime in 10 litres of water. The method of mixing solution is similar to that of Bordeaux mixture. It is a wound dresser and used to protect the wounded portions, cut ends of trees etc., against the infection by fungal pathogens.

Bordeaux paint

Bordeaux paint consists of 100g copper sulphate with 200g lime in 300ml water. It is a wound dresser and used to protect the wounded portions, cut ends of trees etc., against the infection by fungal pathogens.