A grey fungus, Botrytis cinerea or Botrytis, that affects wine grapes. It is also called Botrytis bunch rot. The fungus gives rise to two different kinds of infections. The first, grey rot , is the result of consistently wet or humid conditions, and typically results in the loss of the affected bunches. The second, noble rot or Edelfäule in German, occurs when drier conditions follow wetter, and can result in distinctive sweet dessert wines.

Botrytis cinerea is characterized by hyaline conida on gray conidiophores. The fungus produces sclerotia as survival structures. The fungus germinates with water at a temperature of 18 degrees Celsius.