Managing Powdery Mildew During Veraison

Riping Chardonnay grapes



One of the challenges of grape growing is that of controlling powdery mildew or botrytis after the grapes start developing their sugars (veraison). During the growing season we use elemental sulfur, but as we get within 5-6 weeks of harvest, we must stop. The sulfur is known to leave a residue on the fruit, which also stops fermentation. (Any pesticide or fungicide sprayed leaves a residue on the grapes, a very good reason to consider Biodynamically or organically grown grapes in wine. Know what your growers are using. )

In Biodynamics we use a fermented tea from equisetum, a plant source of silica, throughout the season, which makes it possible to use less sulfur and to keep spraying the tea throughout and after the harvest season. The difference between sulfur and this tea is that instead of killing the spores of mildew (sulfur), the tea encourages the death forces of fungi to stay on the ground, where they belong, not on the fruit. This brings balance.

It is another example of the lessons we learn as we farm this way. We cannot eliminate death forces without actually increasing them later on! Better to work at bringing balance within the vineyard, so the fermentation of the grapes later on is able to proceed, another balance of working with processes of life and death.

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