By Joolz2008
Cleveland,
United Kingdom 
my grape vine has developed grey mould.no pictures yet. it is powdery grey substance that has covered all the leaves and left an ashen grey powder all over the greenhouse.
15 Aug, 2012
Answers
Yup powdery mildew follow TG's suggestions
15 Aug, 2012
Our outside placed grapevine developed grey mould (mildew) one really dry, hot year Joolz. Took some advice, before we were on GOY, and gave it a good watering and it slowly cleared. Maybe your vine gets a bit underwatered in the greenhouse and this lets in this mould disease. Is root inside or out of greenhouse.? If there are grapes you can't really spray if you want to use them.
16 Aug, 2012
The mildew will affect the grapes if there are any - you can get sprays that are safe to use on fruit.
17 Aug, 2012
My guess is, it is Powdery mildew!
see here; http://www.thegardenersalmanac.co.uk/Data/Grape%20problems/Grape%20Problems.htm
15 Aug, 2012