Tuesday, February 15, 2011

Winemaking behind the scenes... Botrytis

NOBEL ROT IN SEMILLON GRAPES IN FRANCE.

Botrytis cinerea is a bunch rot of grapes and is one of the most important fungal diseases of grapes worldwide. You see it mentioned on wine labels - but in truth it is a grapevine disease that most growers frown upon.

The fungus causes two different kinds of infections on grapes. The first, grey rot, is the result of consistently wet or humid conditions, and results in the loss of the affected bunches. Yucky.

BOTRYTIS IN SHIRAZ.
The second, noble rot, occurs when drier conditions follow wetter, and can result in distinctive sweet dessert wines.

The 'bad' Botrytis happens when vineyards get heavy rain before harvest and is most severe where excessive nitrogen has been used, where air circulation is poor, or where an insect pest called Light Brown Apple Moth or other factors have damaged bunches.

Rotted berries - right - typically have a grey cast of the fungal growth and spore-bearing structures which gives the disease its common name - grey rot.

My viticulture blog -  http://djsgrowers.blogspot.com.au/ - contains for information about botrytis and other grape issues.

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