Botritis is a fungus which affects grapes of the species Vitis vinifera, the European wine grape. It infects the grape clusters and inserts its hyphae into the grapes themselves. In large amounts, it will dehydrate the grapes completely and make them worthless. In small amounts, it can actually strengthen the flavor of the grapes by increasing their sugar content, making for better wine. There has been little to no success with either introducing or removing this fungus in the vineyard, although sometimes it can be added to grapes after they are already picked.

since this fungus can be beneficial, it is sometimes known as noble rot.

The Genus Botrytis, is a member of the fungal Kingdom. Members of the Botrytis cinerea species complex, are most famous for their infection of certain grapes, and the chemical contributions they make to late harvest wine flavors. Paradoxically, the genus is also well known for the destructon of harvests.

In autumn due to the 'humidity + temperature = fog' equation, a noble rot forms on the surface of undamaged grapes while the sugar content reaches over 17%. Mycelium perforate the skin of ripe grapes, absorbing the liquid contents rich in tartaric acid and sugar. The grapes dehydrate, the juices concentrate until the grapes are bluish black and intensely sweet.

There are several botrytized wines, the most famous being from white grapes as reds don't seem to support the growth in its noble form well. The top three are:

Enough about wine, more about fungus. It should be noted though that B. cinerea's range is much, much larger. Infecting a wide variety or herbaceous and perennial plants including apples, tomatoes, blackberries, strawberries, lettuce and onions. Also many ornamental plants such as African violets and tulips. In fact, if you find grey mold on your produce there is some chance it is Botrytis sharing the spoils of harvest. It has such low host specificity under the right conditions it can infect almost any dicot and number of monocots.

Tissue specificity: The fungus can infect any part of the plant host except the roots. Though the fungus prefers to attack a different specific part of a plant depending on the host.

Appearance. To the naked eye its all gray. The gray mycelium of Botrytis with gray spores form fuzzy or fluffy patchy growths of grayness. Under a microscope you can see where Botrytis gets its' name, from the fact that the clusters or condiophores look like little bunches of grapes.

Why Botrytis causes infections. Botrytis is often an opportunist and takes advantage of situations where there is stress or damage. An open wound or overcrowding, vulnerability of a potential host increases with density. It can be mentioned that the situation is less common in uncultivated plants so it is hard to imagine the scope of the damage in the wild.

When reaching epidemic proportions, death and decay swell the airborne spore count until even healthy individuals are susceptible to infection via old tissue. In crops, new infections often occur each year because of the amount of dead tissue still harboring active, viable mycelium, this is another example of the infection as a marker of 'overcrowding'. The living nestled among the corpses of the dead.

This fungus thrives in humidity and where there is a lack of air currents. A trademark other than the silver grey spore masses is that it leaves shiny black specks in the diseased tissue. These are Sclerotium, vegetative survival capsules, the consistency of little stones, that allow the fungus to last out the winter, to rise again producing new host seeking mycelium in the next season.

Taxonomy
KINGDOM: Mycetae (fungi)
DIVISION: Eumycota
SUBDIVISION: Deuteromycotina (The imperfect fungi)
CLASS: Hyphomycetes
ORDER: Hyphales (Moniliales)
FAMILY: Moniliaceae

Some species other than Botrytis cinerea include B. tulipae, B. paeoniae, B. allii, B. byssoidea, and B. squamosa.

sources of note
http://www.ronbergerwines.com/lh_riesling99Napa.htm
http://plantclinic.cornell.edu/FactSheets/botrytis/botrytis_blight.htm

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