Could Green Algae Give Copper Spray The Blues?

One of the biggest threats to vines are fungal infections.  The two most notorious are Powdery and Downy mildew, the former growing in warm and humid conditions, the later in the cool and damp. Either way at some point in the year if you’re in a marginal climate, like Bordeaux for example, you’re in danger of one or both.  And current treatments are contentious.

The copper compound treatments used, known as Bouillie Bordelaise, have been around for nearly a couple of centuries.  The hard metal solution acts as a buffer to stop fungal spores taking hold of the leaves. This is the famous blue powder you see across vineyards across the world.


On the upside it is not absorbed directly by the vine, so doesn’t necessarily count as an agrochemical.  To a certain extent this is good for organic and biodynamic producers, as they’re technically allowed to use it to fend off fungi.  But its impact on the soil is up for debate and with a reduction in organic life and eutrophication in streams and rivers being laid at its door.

So the testing of an algae found naturally on the shores of the Atlantic Ocean is peaking interest in the organic/biodynamic community.  Sophie Kevany, writing in Decanter, cites work done over the past three years by researchers Lionel Navarro and Laurent De Crasto.  On a practical study at vineyards across Bordeaux and Cognac, the algae has been 100% effective in stopping both mildews, and a 50% success rate in stopping grey rot.

This is big news.  If successful trials continue at the Châteaux, including Margaux’s Dauzac, then the pair will look to generate a commercially available product by 2022.

That’s just 2 years after the whole of Saint Emilion will have to be practicing sustainable viticulture or they’ll be demoted to Bordeaux AOC.

So good to see Bordeaux, for many years the pariah of positive change in the wine making world, coming to the forefront of the next stage in making these gorgeous liquids ecologically viable for years to come.

Organic and biodynamic producers can sleep a bit easier at night too.




Picture from Sophie Kevany’s Decanter article, available here



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