Botrytis cinerea is a fungus that can infect grape berries and other plant tissues. In vineyards, its effect depends heavily on weather and grape condition. Under certain conditions it causes destructive grey rot; under a more specific pattern of humidity followed by drying, it can develop into noble rot, which is used to produce some of the world’s most famous sweet wines.
Grey rot occurs when infected grapes remain wet and decay, often producing grey fungal growth, damaged berries and undesirable flavours. Noble rot can develop when ripe, healthy grapes experience humid conditions that allow infection followed by dry, sunny or breezy weather that encourages controlled dehydration. The berries shrivel and concentrate their sugars, acids and flavour compounds.
Botrytis can contribute aromas of honey, apricot, marmalade, saffron, dried fruit and spice. It may also influence acidity and texture. The final result depends on grape variety, vintage, infection level, harvest selection and winemaking. Botrytis is not automatically beneficial; poor or uncontrolled infection can spoil the crop.
Botrytis is central to many Sauternes and Barsac wines in Bordeaux and can be important in Tokaji Aszú from Hungary and selected German and Austrian sweet wines. The grape varieties and production methods differ by region.
Example: in Sauternes, Botrytis may affect Sémillon and Sauvignon Blanc grapes, concentrating them for the production of sweet wine with high acidity.
Botrytis is a specific fungal pathogen, while sour rot involves a broader microbial complex and can create vinegar-like aromas. Vineyard sorting and selective harvesting help remove damaged fruit and preserve wine quality.
Chef’s note: Botrytis is the organism; noble rot is the beneficial expression under suitable conditions. The terms should not be used interchangeably.
This term is one of hundreds covered in depth across OCS courses, learning paths, and 1-on-1 coaching with Chef Eric.
