Botrytis cinerea is a necrotrophic fungus that affects many plant species, although its most notable hosts may be wine grapes.

The second, noble rot, occurs when drier conditions follow wetter, and can result in distinctive sweet dessert wines, such as Sauternes, the Aszú of Tokaji, or Grasă de Cotnari.

[citation needed] The fungus is usually referred to by its anamorph (asexual form) name, because the sexual phase is rarely observed.

"Botrytis" is derived from the Ancient Greek botrys (βότρυς) meaning "grapes",[2] combined with the Neo-Latin suffix -itis for disease.

The causal agent, Botrytis cinerea can infect mature or senescent tissues, plants prior to harvest, or seedlings.

[7] These conidia are asexual spores that will continue to infect the plant and surrounding hosts throughout the growing season making this a polycyclic disease.

Botrytis cinerea is characterized by abundant hyaline conidia (asexual spores) borne on grey, branching tree-like conidiophores.

[citation needed] Overexpression of the gene atrB produces altered versions of the transcription factor mrr1, which in turn confer a multiple fungicide resistance phenotype known as MDR1.

[10] Temperature, relative humidity, and wetness duration produce a conducive environment that is favorable for inoculation of mycelium or conidia.

[11] Controlled environments, such as crop production greenhouses, provide the moisture and high temperatures that favor the spreading and development of the pathogen B. cinerea.

[12] Humid conditions can result from improper irrigation practice, plants placed too close together, or the structure of the greenhouse not allowing for efficient ventilation and air flow.

A distinct fermentation process initially caused by nature, the combination of geology, climate and specific weather led to the particular balance of beneficial fungus while leaving enough of the grape intact for harvesting.

The Chateau d'Yquem is the only Premier Cru Supérieur Sauternes, largely due to the vineyard's susceptibility to noble rot.

Botrytis produces an anti-fungal compound that kills yeast and often results in the fermentation stopping before the wine has accumulated sufficient levels of alcohol.

The infection also affects rhubarb, snowdrops, white meadowfoam, western hemlock,[17] Douglas-fir,[18] cannabis,[19][20] and Lactuca sativa.

[citation needed] Botrytis cinerea mold on grapes may cause "winegrower's lung", a rare form of hypersensitivity pneumonitis (a respiratory allergic reaction in predisposed individuals).

[6] Not planting cultivars that have an upright or dense growth habit can reduce disease as these limit airflow and are favorable for the pathogen.

Pruning or purposeful removal of diseased, dead, or overgrown limbs on a regular schedule can also help to improve air movement.

[7] Sanitation by removing dead or dying plant tissue in the fall will decrease inoculum levels as there is no debris for the sclerotium or mycelia to overwinter.