Under which circumstances is grey rot considered noble rot?

• A. Grapes are fully ripe
• B. Humid, misty mornings followed by sunny, dry afternoons
• C. Both grapes must be fully ripe and humid, misty mornings followed by sunny, dry afternoons
• D. None of the above

Answer: (C)

Noble rot occurs when Botrytis cinerea colonizes ripe grapes under a specific microclimate: morning humidity or mist allows the fungus to take hold, while warm, sunny afternoons dry the grape skins and concentrate sugars, acids, and flavors as the berries desiccate. The fruit needs to be fully ripe so there’s enough sugar and acidity to balance the concentration created by the mold. If the climate lacks the drying sun, or the fruit isn’t ripe, you don’t get the desirable botrytized wine and instead risk ordinary grey rot or a failed harvest. Therefore, fully ripe grapes plus humid, misty mornings followed by sunny, dry afternoons define noble rot.