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What's wrong with my grapes?

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Electrojim

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I have tremendous luck with Concord grapes for jelly, but my Zinfandel vine obviously has problems. I get good green clusters, which begin to ripen nicely, but when they get to a Brix of about 13 or so, the grapes begin to shrivel. A few clusters continue to mature, but far too few to do anything with. So for the second year now, I simply cut off all the grapes and put them out for the garbage collector. I've attached a couple of snapshots of the grapes as seen yesterday.

Grapes1.jpg
Grapes3.jpg

I looked at some photos of 'grape diseases' on the Web, but didn't find anything that approximated my situation. My leaves, stems and trunk are very healthy, and the Concords, planted adjacent, have no problem at all.

When I cut my poor, sick clusters off, they were light as a feather. In other words, the grapes that look shriveled are totally desiccated. The few grapes in any cluster that look healthy taste just fine, and as of their harvesting (for the garbage heap) had reached a Brix of about 20.

I'm really disappointed and sick about this; if anyone has a fix I'd be grateful.
 

balatonwine

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First photo: Zinfandel is infamous for not having consistent full cluster ripening. If you wait for some green berries to ripen, the others may start to go to raisins, especially if you have warm weather.

Second photo: Looks like "Nobel Rot":

https://en.wikipedia.org/wiki/Noble_rot

Nobel rot is not necessarily bad -- it can increase brix, but it will decrease wine yield. Consider picking soon.
 

salcoco

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I would visit some local vineyards and discuss this problem with them. I think a spray program will fix your problem.
 

Electrojim

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Thanks very much for the tips, all. TOMMARINI, you ask if I spray. Never have, but certainly not opposed, if the spray isn't too toxic. What is generally recommended? I know nothing about this.

20 years ago, when I lived about 350 miles further north in a coastal mountain community, I grew Zinfandels and never had this problem. The leaves on those vines got what looked like 'buckshot bumps,' but the fruit was just fine and all ripened nicely in sync. With the one vine I have now I was hoping to make a couple of gallons of wine. I'll try again next year, but sure want to fix anything that needs fixing before next season.
 

balatonwine

The Verecund Vigneron
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Thanks very much for the tips, all. TOMMARINI, you ask if I spray. Never have, but certainly not opposed, if the spray isn't too toxic. What is generally recommended? I know nothing about this.
You can control bunch rot/noble rot with potassium bicarbonate. Very non-toxic. Commercial sources include Armicarb.

20 years ago, when I lived about 350 miles further north in a coastal mountain community, I grew Zinfandels and never had this problem.
The affects you see are probably site and local environmentally determined. See this for more information:

https://en.wikipedia.org/wiki/Zinfandel#Viticulture_and_winemaking

The leaves on those vines got what looked like 'buckshot bumps,'
Probably grape leaf blister mite.
 

TOMMARIANI22

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Thanks very much for the tips, all. TOMMARINI, you ask if I spray. Never have, but certainly not opposed, if the spray isn't too toxic. What is generally recommended? I know nothing about this.

20 years ago, when I lived about 350 miles further north in a coastal mountain community, I grew Zinfandels and never had this problem. The leaves on those vines got what looked like 'buckshot bumps,' but the fruit was just fine and all ripened nicely in sync. With the one vine I have now I was hoping to make a couple of gallons of wine. I'll try again next year, but sure want to fix anything that needs fixing before next season.
I would use a product called oxidate it's a hydrogendioxide mix for plants and grapevines in general. Gloridfied hydrogenperoxide. It is excellent though it is not a Harley treatment and it kills everything and I mean everything it comes into contact with. Itd be a great tool for you because you don't need to constantly spray .. if disease pressure is up spray every five days. It is only a contact spray after 24 hrs it is no longer effective but for your circumstances it is a great preventative and will absolutely help you with summer rots such as this. Zinfandel is huge on rotting for no apparent reason.. be caeful how much you water. Zinfandel likes to displace excess water in those berries which causes them to burst and expose itself to fungus.
 
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