Shrivelling cluster

Grape    None Given

My Valliant grapes (in Manitoba, Canada) have been producing wonderfully well every year. But each year there are some clusters that get something I thought was sunburn and eventually shrivel and dry up. This only happens to a few grapes of the cluster. Not nearly all clusters get this. I don't believe it is sunburn as there are also some that are not in the sun at all. The leaves and stem are perfectly ok. I have attached the picture. Any advice would be greatly appreciated.

Posted by: Bw (1 point) Bw
Posted: July 28, 2016



it doesn’t look like a disease (i.e., black rot) also if it was black rot the leaves should had necrotic areas.

From the picture it does look like sun burn (my first guess) or physical damage, for example berries injured during management operations. Also the shoot in picture looks broken.

I would exclude a physiological /ripening disorder, called berry shrivel, because the symptoms show up immediately following veraison, and your Valliant grapes are still green.
Similarly the symptoms of another shriveling disorder called bunch-stem necrosis (BSN) develop weeks after veraison with necrotic lesions on the rachis.

You wrote that this happen every year. I was wondering if the affected clusters keep ripening (accumulating sugar) to harvest or not.

I hope this helps

Michela Centinari
Assistant professor of viticulture
Penn State University

Posted by: Michela Centinari (2 points) Michela Centinari
Posted: August 1, 2016

Thanks ever so much for your input, Michela. I really appreciate it. The grapes are looking great once again this year with just the odd cluster having some of those shrivelled grapes. Overall the vines and all are perfectly healthy, so I agree that it is not a disease, rather something minor such as sunburn.

Quick other question:
Two vines out of my 100 are having yellow turning leaves. Some even turn brown and start drying. Could they be lacking anything? I could also send a picture if you like.

Posted by: Bw (1 point) Bw
Posted: August 3, 2016

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