I have suffered powdery mildew for the last three seasons (Black Hamburg)
but believe that I have now found a remedy.
Before launching into the preparations for the next season, a question. I
have read although never practised it , that next season's grapes grow on
last seasons growth. Last season's growths are on the previous season's
growths, and this could go on forever.
Have I misunderstood?
Alistair

In article , Alistair Macdonald
writes
I have suffered powdery mildew for the last three seasons (Black Hamburg)
but believe that I have now found a remedy.
Before launching into the preparations for the next season, a question. I
have read although never practised it , that next season's grapes grow on
last seasons growth. Last season's growths are on the previous season's
growths, and this could go on forever.
Have I misunderstood?
Alistair

Yes and no. Grapes do grow on the previous season's new growth, and that
new growth will grow on existing stems of any age. How and where that
happens will depend on how you carry out your winter and summer pruning,
but none of that is directly connected to your mildew problem.

There are many methods of grape vine pruning; in most cases a lot of it
is done to prevent the vine/s from taking over the greenhouse as well as
encouraging better quality fruiting. In my system, I keep a main stem in
place over the centre of the greenhouse, that throws out a lot of new
growth each year, it also develops lots of grape bunches, the best being
on last years new growth, as you have already mentioned.

In summertime, a lot of new stems appear, along the main stem and as
extensions to shorter pruned stems which are carrying bunches. Much of
the new growth needs to be pruned back, leaving two fruiting buds on the
ones which are to be left in to carry next year's crop. For winter
pruning, all further new growth needs to be pruned out as soon as the
grapes have finished being picked. which is about now.

In some years I see evidence of mildew building up. For that I use
fumigation sulphur candles in November when the vines are fully dormant.
At the same time I may also paint the pruned stems with Bordeaux
Mixture, something I would not use on an actively producing food plant.
I collect up all leaves and pruned stems and burn them, I also rake over
the greenhouse floor to pick up any remaining diseased material from the
affected vines before carrying out the anti-mildew treatment. Those
treatments usually give 3-4 years protection against vine diseases
before they need to be repeated.

Materials can be purchased online from: www.OrganicCatalogue.com
--
Alan & Joan Gould - North Lincs.