Strange coloration on grape leaves?

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grapenoob

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Hello everyone,
I have a red flame grapevine planted about 6 years ago in California, and it is growing very vigorously.
Recently, leaves near the top have been getting this strange coloration where there are large patches of yellow with a small brown dot in the center. This has never happened before.
Can anyone help with identifying the cause of this problem, and what I can do to save it?
 

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Jim Welch

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I know nothing about growing grapes. But I do know that many plants can develop yellow spots from nutrient deficiencies in the soil, specifically minerals, have you fertilized at all?
 

grapenoob

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Yes, I've fertilized. I thought it was black rot at first as well, and maybe it is, but the splotches don't really look the same. In the online pictures the splotches are darker near the outside, but here they are sort of uniform in color and actually kind of fade to green instead of being a sharp contrast.
 

Dennis Griffith

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I would say you have Anthracnose setting in. If you have a small operation (50 vines or so), I recommend a mix of Immunox and Serenade. If you have a large operation (like 1000 vines), then Sovran may be a better fit.
 

Dennis Griffith

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I'll throw this in as I had someone tell me that the spots weren't going away. So, once leaves get these spots, they have them. The treatment is to keep new leaves from getting them and to keep the current spots from progressing. Left untreated, the spots will continue to get larger and vines will eventually shed the leaves in an attempt to get rid of the issue.
 
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