There Bordeaux mixture it is the oldest of the biological anticryptogamics for plant care and today it can be found on the market in industrial preparation ready for use. However, it can be easily prepared on your own as it is a simple mixture of copper sulphate and lime hydrate.
Before starting work, however, it is better to know a few things. Of the two ingredients of the Bordeaux mixture, the active one is copper sulphate which, being a very acid salt, needs to be diluted with the addition of calcium hydrate present in the lime. The latter also serves to give persistence to the effect.
The action of the Bordeaux mixture it depends on the percentage in which copper sulphate and calcium hydrate are present: if the former prevails, the compound will be more aggressive but also of shorter duration; a greater presence of calcium will instead make the action milder but more lasting over time.
Another useful thing to know about Bordeaux mixture is that it should be used immediately after preparation because its effectiveness is reduced over time. However, be careful not to exceed the doses because in certain cases the excess can cause damage to the more sensitive varieties.
With the Bordeaux mixture Many fungal and cryptogamic diseases are prevented and treated such as alternariasis (carrot, cabbage, potato, tomato, pore ...), anthracnose, downy mildew, septoria and scab (especially of pear and apple trees).
Finally, here is the traditional method of preparation of Bordeaux mixture. Pour 90 liters of water into a non-metallic container and, stirring, add 1 kg of copper sulphate. You will understand that the copper salts have dissolved when you see the water turn a homogeneous blue color.
In another container, pour 10 liters of water and add 700-800 grams of calcium hydroxide, stirring vigorously until the powder has completely dissolved. At this point, combine the two solutions by pouring the second into the first and continue mixing for a long time. As mentioned, the Bordeaux mixture should be used immediately because it keeps little.
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