Question: What is causing this problem
with the leaves on my grape vine?
Answer: My first guess would be Esca.
Its a disease/disorder that no real causal organism has
been identified. Seen a couple of other cases pop up in
the past two weeks. Some feel it is some type of mild pathogen
that shows symptoms when some other stress induces them.
If it is in a commercial planting, it would probably be
best to remove the plant. I have seen it disappear or appear
in the same vine only every two or three years. Most people
get fed up with it and pull the damned thing and replace
it. Not soil borne, so replanting is definately an option.
The other possibility is that it is caused by solvent or
petroleum toxicity. Gasoline leak, oil change, etc can give
the same type of leaf burn.