Bordeaux châteaux test algae to fight mildew

Bordeaux châteaux test algae to fight mildew

Tests at 10 vineyards in Bordeaux and Cognac aim to discover whether wine producers could use algae from the Atlantic ocean to prevent fungal infections harming grapes.

Early results from tests at four vineyards in Bordeaux and six in Cognac show that algae could be effective against mildew and botrytis. The research might be particularly useful for biodynamic and organic producers seeking alternatives to copper treatments.

Both fungal infections can pose a significant problem for the area, mainly due to the warm, damp conditions that favour their development.

While the traditional copper solution (known as ‘bouillie bordelaise’) is effective against fungal outbreaks, some producers, particularly those who have embraced organics, have concerns about its toxicity and have long been keen to find another solution.

Enter algae. For the last three years, engineer and oenologist Laurent de Crasto has been working with Lionel Navarro, a researcher with France’s National Centre for Scientific Research (CNRS), to test a treatment using powdered Atlantic algae.

Results to date show a 100% success rate against mildew, and a 50% success rate against botrytis, according to the duo.

Based in the Bordeaux suburb of Pessac, de Crasto said the next steps will be to scale up production, secure regulatory approvals and have a commercial product available by 2022.

Margaux’s Château Dauzac has been one of those testing algae.

Its director, Laurent Fortin, said the original bouillie bordelaise mix was created at Dauzac. ‘So we know all about the benefits and disadvantages. Copper kills everything in the soil. If terroir is saturated there are no bacteria, no worms, nothing.

‘We were looking for alternatives, and this was the most promising,’ he told Decanter.com.

Having started with a test plot, Fortin is now using the algae on all Dauzac’s biodynamic-certified plots, currently about three quarters of the estate.

Looking ahead, he said the aim is to be copper free within five years, with the most immediate challenge being to refine dosages. ‘We had a very wet spring this year, so we had to adapt the percentages and we are still testing and learning.’


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