Mildew on grapes

[granretire]

This is my first year of growing grapes in a greenhouse and I find that many of the bunches are infected with mildew. The door has been open night and day for weeks as has the the roof window. Should I remove all bunches that are infected? I have been removing infected leaves, but I notice that even the stems of the plant have it in places. Guidance please.

[ReformedCharacter]

This is my first year of growing grapes in a greenhouse and I find that many of the bunches are infected with mildew. The door has been open night and day for weeks as has the the roof window. Should I remove all bunches that are infected? I have been removing infected leaves, but I notice that even the stems of the plant have it in places. Guidance please.

This may help - if you haven't already read it...

https://www.rhs.org.uk/advice/profile?pid=569

RC

[granretire]

Yes, I had read it, but it doesn't answer my question about removing the mildewy grape bunches

[88V8]

Belatedly.... yes, remove them but once the mildew has set in the process is pretty inexorable.

The other problem is that the fungal spores will overwinter on the vines, and next year it will all start up again. Commercial vineyards run heavy fungicide spray programmes to control mildew. Timing of the spray is important, as is the ambient temperature.

You could try a thorough tar oil winter wash to reduce the spore carry-over, and to an extent one can minimise the problem by keeping a very open canopy, but realistically once you have an infection, that's it.

A shame to give up after just one year, but I would grow something different in your greenhouse.
Figs?
Kiwi?

Ivor

[Cornytiv34]

Some mould is good. See Noble Rot details here

https://en.wikipedia.org/wiki/Noble_rot
https://winefolly.com/tutorial/they-call-it-noble-rot-botrytis/

I have no knowledge of the types of disease/rot or treatments but it might be worth checking with someone who has more knowledge. Mrs Cornytiv is an RHS member and sends plant samples to them. I do not know if this is available to non members but a telephone call might help.

Mike