What is Botrytis?

Botrytis is often reffered to inside the wine industry by both winemakers and consumers, as noble rot.

That rot term, even with noble in front of it, tends to worry people a litlte bit.  Of course, botrytis is a fungus and in this case a winemaker is allowing, even encouraging it to grow on grapes.  Winemakers encourage its spread by doing a few different things, all of which you'd expect if you were trying to grow a fungus.  First, they tend to keep some level of grass or another ground cover close to the vines, which will keep water.  They then make sure that the grass is wet early in the morning.  Secondly wineries may sometimes have netting or something similar which has botrytis living on it.  By using that netting where they want the Botrytis to grow, they can ensure that it will begin to take hold on the grapes.

At this point, you're probably wondering why a winery or winemaker would want Botrytis, a simple fungus, growing on their grapes.  The answer is that the Botrytis removes excess water from grapes, leaving a combination of higher sugar as well as higher acidity.  That combination, when combined with a winemaker allowing the grapes to pick up even more sugar while hanging on the vine for a longer time period, leads to perhaps the perfect combination if you're making a dessert wine.

The perfect vineyard site for Botrytis is so prized that Chateau d'Yquem in Bordeaux has been granted Superior First Growth status by the French government (their 2nd best classification meaning they feel like it's one of the top 15 vineyards in the famous region of Bordeaux).  That staus has been conveyed almost exclusively because the vineyard at Chateau d'Yquem is susceptible to noble rot, experiencing the phenomenon every vintage, with little winemaker intervention.

At this point, it sounds like a pretty good deal right? Botrytis makes amazing dessert wines, so if you can figure out how to grow the fungus, you might think the wines would be more common place.  A main reason that Botrysised wines are not more common (or really common at all) is that botrytis and yeast (the stuff that causes fermentation or sugar to turn to alcohol) do not get along well.  Fermentation for these wines, is a constant struggle for winemakers.