Ah, the life of a vineyard owner- last week, we were talking about the nice, steady weather pattern of warm, sunny days. This weekend, as you may have noticed, we received over a half an inch of rain with colder than average temperatures. When we experienced rain over the summer, mildew (mentioned a few blogs back) was the enemy to worry about. Now, with the fruit sugars high and vine fatigue setting in, we are concerned with another villain- Botrytis cinerea or gray mold.
Calling Botrytis cinerea a villain isn’t quite accurate- it’s more like Two-Face from the Batman comics (can you tell I have kids?) in that it has both a good side and a bad side. Botrytis infestation is actively encouraged when one is looking to make a botrytisized white wine, such as an ice wine, as it is the mechanism that produces a fine, sweetly concentrated dessert wine- in fact, an infestation in this case is referred to as “noble rot”. However, in most cases, it just causes a lot of headaches and stress for winemakers. In both white and red varietals, infestation will lead to poor color development and stability issues in the wine, with the effect being more pronounced in reds. Most critical after a late rain in staving off a Botrytis infestation are the follow-up temperatures and the wind. If the temperatures bounce back up into the 80’s with low humidity and a drying breeze within a day or two, then everyone can keep calm and carry on. If the temperatures stay low and humidity stays high, then stress and intense observation rule the day. The worst case scenario is if the rain continues, as there are greater foes to deal with then- bunch rot and the vines thinking winter has come, so they start shutting down. That’s the signal to round ’em all up and bring ’em in- even if they aren’t at optimal sugar.
The good news is the weather is looking better, our harvest is well-over halfway done, and the varietals we grow are not very susceptible to Botrytis. Most likely, all that will come of the weather hiccup is that I got the opportunity break out my Latin and use a comic-book analogy to talk about a type of mold.
photo by Anne-Sophie Walker at INRA