Botrytis cinerea

Botrytis cinerea is a mold that significantly impacts winemaking and is known by two distinct names depending on its effect: noble rot and gray rot.

Noble rot

In ideal conditions, when humid and misty mornings alternate with dry and sunny afternoons, Botrytis cinerea causes a positive process called botrytization. This process is key to producing high-quality sweet dessert wines such as:

Sauternes in France, Tokaji Aszú in Hungary, and Beerenauslese with Trockenbeerenauslese in Germany and Austria.
Noble rot causes grapes to lose water, concentrating sugars, acids, and aromas. The resulting wine is characterized by rich sweetness, complex aroma, and balanced acidity.

Gray rot

In unfavorable conditions, especially during prolonged humidity and lack of sunshine, Botrytis cinerea causes a harmful infection known as gray rot. Gray rot can lead to grape rot, significantly reducing crop quality and yield. In such cases, the mold attacks the grapes, causing them to soften, brown, and become inedible.

Botrytis cinerea is thus a mold with a dual character: it can be either harmful or extremely beneficial depending on the conditions in which it occurs. Its proper control and use are crucial for producing some of the world's best dessert wines.

More about botrytized wine is written here.