What's wrong with these leaves?

[Dennis Griffith]

Garden Tech Liquid Sevin has a PHI of 1 day, and will kill those little pests.

 

[balatonwine]

I notice that they didn't test Boron.

Unlikely to be the problem. Boron deficiency has a completely different set of symptoms. Mostly noticed when it affects berries and young leaves:

http://www.omafra.gov.on.ca/IPM/english/grapes/plant-nutrition/boron.html

 

[balatonwine]

The vines were neglected and only dusted a couple times with sulfur. I just started getting involved with managing the vineyard and creating an ipm program.

A vineyard that was so neglected from an inadequate spray schedule is far most likely then suffering from pest issues. Those grape vine leaf hoppers may certainly be a contributing factor. As may be fungus issues. Am leaning toward this not being a nutrient deficiency. If one grows susceptible varieties (ie. all Vinifera varieties) you have to spray appropriately for one pest or another. There is no way around it. It can not be neglected.

Also, depending on where you are, sulfur dusting alone may not be enough. Downy mildew, for example is not controlled by sulfur. A proper IPM program is good to do. But will only help for next year. The damage is done this year.

I did not neglect my vineyard, but we had a lot of rain. And I spray organic only. That is a tough combination that does not always mean good success. And so I had a considerable amount of downy and black rot. Some of my vine leaves have some slight fungal damage. Similar (but less severe) damage as yours.

I have no nutrient deficiency issues for the vine in the below photo, only fungal damage: