What insect/disease leaves peelable, brownish gray, irregular shaped, angular...
What insect/disease leaves peelable, brownish gray, irregular shaped, angular edged, patches on grapevine leafs? I have seen this on the top and underside of the leafs on both my vinifera and frontenac grapevines. In peeling back the patches, I do not see any insect eggs and the patch seems to peel off fairly cleanly.
That would likely be a grape leaf miner - here's a link:
There are two types, one makes 'serpentine' tunnels (see photo in above) and another type makes round 'blotches, see:
Neither of these causes economic injury that impacts the crop.