When it comes to viticulture, Botrytis Cinerea is arguably the most important fungus around. Its effect on the quality and quantity of a harvest can be devastating, yet under the correct conditions, it is responsible for some of the very best sweet wines in the world.
What is Botrytis Cinerea?
Botrytis Cinerea is an airborne fruit-infecting fungus, occurring in wine regions across the globe where microclimatic conditions are conducive to its development.
In a few, select, winemaking regions, however, microclimatic conditions are instead suitable for the development of noble rot. Far from being harmful, noble rot is highly desired among winemakers and vital in the production of the world’s finest sweet wines. (Learn more in "Common Vineyard Pests, Diseases and How to Treat Them.")
In cool, humid conditions, Botrytis Cinerea infects grapes, allowing grey rot (also referred to as bunch rot or ignoble rot) to thrive. Grapes, whose skins are pierced and split by fungal spores, wither and soften before a grey mold spreads plague-like throughout the bunch. Once a bunch has become contaminated with this vine disease, the disease can not be eradicated and the grapes must be discarded.
While fungicides can be used to help tackle the onset of grey rot, they are only effective when used in conjunction with preventative vineyard management techniques. Canopy control, through regular and targeted pruning, improves air circulation in the vineyard and greatly reduces the risk of infection.
Noble rot develops in conditions very similar to those that allow grey rot, with a few important differences.
In areas that experience cool, humid mornings but are then followed by dry, warmer afternoons, the effect Botrytis Cinerea has on grapes completely changes.
During the morning, when conditions are perfect for fungal activity, Botrytis Cinerea spores pierce grapes, just as they do with grey rot. When the sun comes out in the afternoon drying the air and increasing the ambient temperature within the vineyard, the activity of the fungus slows to a halt.
Meanwhile, water from inside the grapes evaporate through the holes created by spores, which in turn increases their concentration of sugar, flavor compounds and aromatic compounds. These dehydrated berries can then used for the production of intense "botrytized" sweet wines.
It should be noted that even in regions that are famed for noble rot wines, the correct microclimatic conditions do not occur each year, and it is in no way a guaranteed phenomenon.
The Character of Noble Rot Sweet Wines
One of the significant advantages of producing wines infected with noble rot is the fact that acidity is maintained, resulting in a very balanced sweet wine. Furthermore, the process increases the concentration of a flavor compound called phenylacetaldehyde, which gives the wine attractive honey and ginger flavors and aromas.
Notable Wines Made With Noble Rot
As grapes that undergo noble rot have gone through a period of dehydration, the amount of must that they yield is significantly decreased. Unfortunately for consumers, this decreased yield means increased prices. Prices that are further increased to compensate for high harvest costs, as grapes must be individually selected by trained workers, and multiple harvests in one vintage are often necessary. (Read about "The Hang Time Debate: The Vintner's Battle.")
Despite their expense, botrytized wines are a must-try for any self professed oenophile, owing to their unique flavor profile and vibrant acidity.
Some prestigious examples to look for include: