Info

Bordeaux mixture is a mix of copper sulphate (CuSO4) and quicklime (CaO) used as a fungicide. It’s used as a preventive measure because its mode of action is useless after a fungus has already appeared.

There are some controversy regarding the use of bordeaux mixture due to its excessive use and impact in the environment. It is nevertheless allowed in some parts of the world for organic gardening.

Its effectiveness is unquestionable, another reason to be included here.

Good for:

As a prevention fungicide to several diseases like: downy mildew, powdery mildew, peach leaf curl, blight and apple scab.

Used regularly on grapevines, fruit trees, potato, tomato and cucurbits.

Bordeaux mixture was “invented” in the Bordeaux region of France in the late 19th century. It was botany professor Pierre-Marie-Alexis Millardet who conducted trials in vineyards with this treatment, recommending later this mixture to control downy mildew.

Supplies Needed

Recommended quantities for 100 L of bordeaux mixture (Formula 1 : 1 : 100 or 1%. To prepare 0.5% bordeaux mixture use the same amount of water as the 1%, but reduce the copper sulphate and lime to half).

1 kg copper sulfate

1 kg lime

100 L water

Non metallic container and non metallic stick for stirring (best choices will be wooden or clay).

Preparation

There are several ways to prepare bordeaux mixture. We share one of the easiest.

Dissolve 1 kg of copper sulphate powder in 50 litres of water. Dissolve 1 kg of lime (powdered) in the other 50 litres of water. Add the copper sulphate solution slowly to the lime solution with constant stirring. The bordeaux mixture is ready to be sprayed.

Measure the PH of the mixture, the optimal value is around 7. If it’s acid, you can correct it with lime milk (prepared separately).

P.S. – You can buy ready-made bordeaux mixture to skip the process of dissolving both ingredients.

General Use

Use the bordeaux mixture after preparation. It should not be stored for further use.

Spray plants when it’s not too hot. Best periods are in the morning or when the temperature is low.

Winter treatment – before the end of winter or early spring before flower buds bloom.

Autumn treatment – after the leaves have completely fallen.

Preventive treatment of plants when weather conditions are favourable for fungus diseases development.

Special Care

Use proper PPE.

Do not use bordeaux mixture in combination with any prevention or control method. Allow two weeks interval between treatments.

Because of the controversy regarding bordeaux mixture, we recommend a conscious approach to its use.

Massive and continuous use of bordeaux mix can cause heavy metal pollution affecting fauna, flora and soil.

Be aware that its use is illegal in some countries.

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