Mildewed Grapes

[goldilox]

Think I've got mildew on about half my grapes - they were just starting to ripen too They aren't looking too clever and have a white powder all over them. The leaves don't seem to be affected, and it's just the grapes lower down.

Is there any way of curing this and saving the grapes? I did spray regularly with Bordeaux mixture from spring, but stopped when I stopped spraying the peaches and nectarines.

[yummyveggies]

is it a whitey grey powder a little like you get on Strawberries when they go 'furry' with mould. If so it could be Botrytis - and I am sorry to say I don't think there is anything curative - and like most of the mildews, powdery , downey and Botrytis , most of the sprays are preventative rather than curative - a few of the commercially available ones can have some effect against these mildews - but even these are mainly preventative.

Try picking off the affected grapes and also stripping off the leaves round the bunches to get as much sun and air as poss - though I note you are in the SW of France so probably lovely and sunny.

you are so much further ahead than us - indoor grapes are ripening - but outdoor ones are only just starting to show signs of veraison !
sorry not to be of much use ....
regards

[goldilox]

Don't think it's botrytis, think it's probably powdery mildew. Have been reading up on the internet and it sounds the most probable. Someone recommended spraying them with milk (which I did this morning), but I don't really hold out much hope of that curing the problem. The only treatment I've read about is sulphur, but don't fancy using that on something we're going to eat.

I have cut back the leaves surrounding the bunches, but maybe didn't do it soon enough. Also, they've not been watered as much as I would like through lack of water. Next year will be different!

Anyway, hopefully it won't spread to the rest of them. Interestingly only one plant is affected, the grapes on the other one are fine.

Thanks for the reply anyway yummyveggies - think I just have to put this one down to my own lack of care. A lesson learned!

[yummyveggies]

hi you could try Serenade ASO - this is newly licensed in the UK a biological fungicide from AgraQuest Inc (marketed by Fargro Ltd) for commercial use .
It may be worthchecking if it is available for amateurs in France.

It is a bio fungicide using a selected strain of bacteria bacillus subtilis (strain QST 713) and has no harvest interval - ie you can spray it right up to harvest and it is meant to be good against Botrytis

with regards Sulphur - you can still commercially be considered 'Organic' if you use Sulphur - and there is an element of foliar feed. This link on PM may be useful
http://www.agf.gov.bc.ca/cropprot/grapeipm/mildew.htm

also if you have lots of lush canopy growth watering may not actually be a good idea as it will promote leaf / canopy growth ...

hope this helps ..

[goldilox]

Thanks for the reply Yummieveggies. Sorry for delay in responding, not had much time to check the website lately.

Found the article very interesting, particularly the temperature chart which seemed to indicate that 40 deg over a 6 hour period can kill the fungus. We had 40 deg in the shade of our porch yesterday, so was quite a bit hotter in the sun. Will be interesting to see if they can actually recover at this stage.

Happily, we still have plenty to keep us fed, but next year will be a bit more vigilant with the spraying.

[Tigger]

The French grow roses at each end of their rows of vines because they get 'anything going' first, which gives you a chance to treat your vines. I always thought it was the winemaker's wife's opportunity to incorporate flowers, but apparently not. We've done this and it does seem to work.

[goldilox]

I've got 2 rose bushes growing underneath the vines, and they didn't get it
I'll just have to keep spraying longer next year.