Botrytis Cinerea (Noble Rot)
A fungus that, under specific conditions, concentrates grape sugars and acids to produce some of the world's greatest sweet wines. The beneficial form is called "noble rot"; the harmful form is "grey rot".
In depth
Botrytis cinerea is a fungus that attacks grape skins. Whether it becomes noble rot or grey rot depends entirely on the weather conditions. Noble rot develops when humid mornings (which allow the fungus to establish) are followed by warm, dry afternoons (which cause the fungus to dehydrate the grape rather than rot it). This dehydration concentrates sugars, acids, and glycerol in the grape, producing the raw material for exceptional sweet wines.
The resulting wines show distinctive flavours of apricot, marmalade, honey, ginger, and saffron, as well as a rich, almost oily texture. Iconic botrytis-affected wines include Sauternes (France), Trockenbeerenauslese (Germany), and Tokaji Aszú (Hungary).
Grey rot, by contrast, occurs under continuously humid, wet conditions. The fungus causes the grape to rot and collapse, destroying aromas and producing off-flavours. Winemakers must carefully monitor for grey rot during the growing season and harvest.
At Level 3, candidates should explain the precise conditions needed for noble rot and link those conditions to specific regions and wines.
Related exam topics
Frequently asked questions
- Why is Botrytis called "noble rot" when rot is usually bad?
- Under the right conditions — humid mornings followed by dry afternoons — Botrytis cinerea dehydrates grapes rather than destroying them. This concentrates sugars, acids, and flavour compounds to extraordinary levels. The result is intensely sweet, complex wines. The word "noble" distinguishes this beneficial form from "grey rot," which simply destroys grapes under continuously wet conditions.
Related terms
Practise questions on this topic
Use Vinlecta to practise exam-style questions that test your knowledge of botrytis cinerea (noble rot) and related topics.