Ask Wine Wizard

Knocking Down Rot On Grapes


Morris Carmiche — lThousand Oaks, California asks,

What do you do when your fruit comes in with signs of rot from an unusually wet season?


That’s a great question as we approach the harvest season. Though I don’t expect 2019 harvest to be like 2011 or 1998, many of us all over the country, from Oregon to Pennsylvania, will have to deal with some kind of rot or Botrytis close to harvest time. When I’m potentially faced with it, I get my special cellar treatments ready to go. The below is an anti-Botrytis and rot protocol that I’ve used when Botrytis or rot is what I’d call “medium”, i.e. about 10–20% of clusters seem to be affected. In a situation like that you can usually pick, treat the must or juice, and salvage some good wine out of it. However, if you are buying the grapes, review your contract and parameters for rejecting fruit from growers.

My anti-Botrytis protocol:

  • Reds and whites: Add a higher dose of SO2 at destemming or in the picking bins in the field (I recommend 50–70 ppm total SO2 addition).
  • Whites only (assumes you’re destemming and pressing or just direct-pressing white grapes): Also add 0.20 g/L Lysozyme or Lactizyme mixed into juice tank after pressing (wait at least 1 hour after last SO2 addition to avoid inactivity/binding with SO2.) Hydrate it first in 10 times weight of water at ambient temperature.
  • Whites only: After about 4 hours have elapsed since the Lysozyme/Lactizyme add, add 0.12 g/L PVPP and 0.12 g/L bentonite to the juice tank (the waiting period helps to avoid the bentonite binding w/ proteins in the enzyme).
  • Reds only: 0.20 g/L Lysozyme/Lactizyme in the must at least one hour after SO2 was added to grapes at destemmer.
  • Whites only: Settle the juice.
  • Whites only: Rack clean, taking only light fluffy lees.
  • Reds and whites: Inoculate with a strong yeast like EC-1118 (Prise de Mousse), in a higher than normal rate (~2.5–3.0 lbs./1,000 gal. or 1.1–1.4 g/gal or 0.3–0.4 g/L)
  • Reds and whites: Feed fermentation well (target 300 ppm Yeast Available Nitrogen) but don’t overfeed — you don’t want to feed “bad guys.

Proceed as you would, keeping an eye out for stuck fermentations and elevated volatile acidity. You’ll have an elevated level of unwelcome microbes competing for micronutrients and resources, so keep a weather (pun intended) eye out!

Response by Alison Crowe.