Pictured above is a familiar sight in garden centres and DIY stores throughout France: rows of packs of powder used to produce the best-selling fungicide Bouillie Bordelaise, or “Bordeaux Mixture”. As my knowledge of Bouillie Bordelaise was very slim (I knew that it was blue, but that was about all), I decided to investigate!
First things first, what is Bouillie Bordelaise? As so often, Wikipedia was my first port of call: the introductory paragraph states that the fungicide is “a mixture of copper (II) sulfate (CuSO4) and slaked lime (Ca(OH)2) used in vineyards, fruit-farms and gardens to prevent infestations of downy mildew, powdery mildew and other fungi”. The “preventative” aspect is important as the Wikipedia entry adds that “its mode of action is ineffective after a fungus has become established”. In other words, you have to treat the plants before they fall sick.
Scientists began looking seriously into the matter. One of the most prominent was the ampelographer (vine expert) and botanist Alexis Millardet (1838-1902), a Bordeaux university professor who, in 1882, was out and about in the Médoc wine-growing area when he noticed some distinctly healthy-looking vines in Saint-Julien-Beychevelle, on the grounds of Château Ducru-Beaucaillou. Stopping to enquire, the person who oversaw the land, one Ernest David, explained that Médoc vine-owners had developed the practice of spraying a mixture of copper sulfate and slaked lime on roadside vines to dissuade passers-by from helping themselves to grapes. It got Millardet thinking about the potentially protective properties of the solution.
|The vines and grounds of Château Ducru-Beaucaillou, where the Bouillie Bordelaise story began.|
That recipe remains in the public domain and is as follows (based on the information found here), if you’d like to produce 10 litres of the stuff from scratch rather than purchasing an off-the-shelf pack of readymade powder. First, be sure to stock up on the following equipment and ingredients: a pair of sturdy gloves, one 10-litre bucket, one 15-litre plastic bucket, 300g of slaked lime, 200g of copper sulphate and 10 litres of water.
- Step 1: put on those sturdy workgloves.
- Step 2: using the 10-litre bucket, dissolve 300g of slaked lime in 6 litres of water and stir the mixture with a stick to produce lime slurry.
- Step 3: in a 15-litre plastic bucket, dissolve 200g of copper sulfate in 4 litres of water.
- Step 4: slowly add the lime slurry to the copper sulfate solution.
- Step 5: stir like there’s no tomorrow.
- Step 6: let the solution rest for 24 hours.
- Step 7: pulverize on the desired plants.
|A Ducru-Beaucaillou vine leaf.|
> Find it on the Invisible Bordeaux map: Château Ducru-Beaucaillou, Saint-Julien-Beychevelle
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