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BigH

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First picture looks like potassium deficiency to me, which can be brought on by periods of heavy rain.

H
 

balatonwine

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One would need more information to really help beyond a WHAG. For example, early season fungus damage, can look like nutrient deficiency during late season senescence.

So a few questions:

- What variety of grape is this?
- What was your pest spray schedule, if any (fungicide and/or insecticide), and what products did you use?
- What was the weather like this year? Dry? Very wet? Etc.
- Is this issue affecting all plants, or just some?
- Is this issue recent or did you notice this or any other issues with these vine's growth during the spring or summer? (Nutrient deficiency is often first noticed as a spring and summer event, during plant growth, not really so much a late summer/autumn event).
 
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justinb

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-This is Itasca. I also have Marquette and Petite Pearl that seem to be unaffected.
-I did not spray anything except Sevin for the beetles
-Wet all year
-This started a month ago and is getting worse. Before this, everything has bee fine. A few cordons have shriveled and died off.

I can take a few more pics if it helps
 

askins3097

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Did they start as yellow spots? I’ve been fighting Downey mildew on two of my six Niagara vines and it starts as yellow spots, then looks similar to this.
 

Dennis Griffith

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If it's a potash deficiency, then you can get that at about any garden center (or Amazon). It would be best to get the soil tested so that you know where you stand,
 

marquettematt

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Did you fertilize this year? with what?

Supposedly Itasca is resistant to mildews. At least that's what Double A and U of Minn claims. Was there any black rot this year?

How recent are those pics? For this time of year, the canes look way behind on hardening off.
 
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