All the white stuff on the undersides of the leaves is due to the erineum mites.

It's not mold.

In time, it will slowly change color from white to tan to a medium brown. All due to the mites.

Thank you, Jean. I will try to circle the white in the actual clusters. That's my real question. I only showed pictures of the blister mites to show the health if the leaves

Has anyone seen this happen before?

Did you spray them? It must be done before it shows up.

No....this is the first year It's actually grown grapes and has had blister mites. Spray it with and for what?

That might be galls from the mites.

I get tumid gall maker some years

Mites run rampant through the wild vines in the woods but don't do serious harm.

I'm in brooklyn. I have had several grape vines, still do have 2, working on a new 3rd, I had something like that blistering on some vines only like first pics in leaves on one particular vine type but never galls on fruit. I would see it when my canopy got too thick mostly or we had too much rain/humidity. I would pull every leaf that looked like that and any contaminated fruit too for disposal not compost. Open up the vine and fruit to greater sunlight, don't shade fruit. Rain weather coming back soon to NYC. I'm not sure if those mites prefer wet or dry but we had unusually very wet spring, get more light into the situation and you can spray insecticidal soap for mites, probably need copper or fruit tree spray. I had bad mites another spring on fruit trees when it was too dry, the chemical that worked the best was a cold garden hose washing the plant daily. Someone familiar with the mite in question might know better. I never spray grapes, I have tiny tiny white spiders that come with the yard and live in my vines do the work for me. I even recognize their egg cases. Good luck

What age/variety of grape is that and how is it grown (Trellis, wire, fence)? Some of these newer hybrids are not hardy for our urban neck of the woods.

Sorry for taking so long to reply back!

I do not know the variety. I didn't plant it and it's never given fruit before to even know the color of the grape.

Age? I would say over 10 years old. Doing in poor condition because it was never maintained. I may have mentioned this already. I started making a trellis for it and trained it to it and its the first year we really had any of these problems. Other years the leaves were perfect to use for stuffed grape leaves.

Im thinking I should prune it down as much as I can. This way I get rid of the blister mites and it can send out new shoots. How much of it can I prune and how far down without doing permanent damage?

A vine should be producing by the 3rd or 4th year its in the ground. They do have newer and older varieties to choose from, a consideration.....and they all make leaves.......You get grapes on whatever grew the year before - one year old wood. So cut out all old 2 year and up wood and any infected new wood (this year) except for main stalk up to trellis and a main runner on top of the trellis, dispose of and do not compost any trimmings. Try to save some new one year wood (this year) for next years fruit.

This is the whole grape. Its two grapes. When it sprawled on the ground, one of the vines rooted and I cut it to split them.

Where would I start? looks like it may also be in a bad spot with that tree nearby, grapes need sun.

The Trellis is too flimsy, you need something more substantial that that that is fully braced together on top so a top vine can ride on it. Mine is galvanized steel. Treated wood works too or redo and add more bracing. Once you reset your posts you can just string wire across the top. For ten years old that main brown stalk coming out of the ground is no big deal. My neighbor has that same nasty weedy ground cover. I would only keep the main stalk up to the top of the trellis and ONLY let new growth fill in the top and extend across the trellis. Get rid of everything below that. The vine should be spreading out horizontally to get maximum sun with grapes hanging down.

It looks like its in a bad spot, but that area gets sun for most of the day.

Yeah, its flimsy and falls often. I never glued it together and haven't added more PVC to go across the top for support. Been a little lazy with it. What do you mean by resetting the posts?

So I should cut everything but the wood growth and restart training next spring/summer? Should I spray the wood with anything?

I wouldn't spray until after leaf fall - and before spring buds pop, and any good general all purpose product for fruit trees including lightweight horticultural oil will work. The trellis has to be sturdy and fixed, the posts look crooked and undersized in diameter, if that's 1-1/2" diam (who knows) I'd be using 2" diameter, you can use smaller for bracing. Remember that the trellis has to last 30 years and carry significant weight over time once heavy branches are resting on it, you do this once the right way. If you do the trellis now, you can start training now with whats left of the season. Yes just keep the brown main stalk vertical and maybe the highest green horizontal branch (one) if it'll fit on top of your trellis when you put in a top.

One grape vine per trellis, relocate or can the other

Any specific material you would recommend for the trellis? I read that a simple PVC frame would be good and cheap. I can repurpose the PVC pipes for a cucumber trellis with holes and twine.

treated wood on a concrete footing, heavier PVC, galvanized steel threaded pipe, its up to you

The cheapest option. Thats why I went with PVC pipes.

If you build a good trellis, however you do it, that's a start

I cut all the green vines and left the wood. Now the parts that I cut are "bleeding"

The bleeding is normal, the wound should scab over in a couple days.

Not sure why you need a trellis when you have a chain link fence that would be plenty strong right behind the plant.

Clear maybe a foot or two of the morning glory and Virginia creeper and get the main trunk to the top, then train a couple laterals left and right.

In the future you will need to leave some of the green shoots to harden off and be your fruiting wood next year.

Bklyn citrus is right on most of his suggestions, (all my posts are sunk in the ground without concrete). A full crop of grapes are very heavy. This time of year I'm scouting for broken posts and wire. Each plant can give 20-50 pounds of grapes, depending on variety.

From the pictures of the wood the plant appears only 4-5 years old. Unless it started back over from the ground.

Bleeding is normal and will heal. I'm not a fan of joint fences for grapes unless there is easy access from both sides (my neighbor and I are friends and I short hop see pic). A small concrete footing is for galvanized pipe or treated wood trellises only. I'm not a fan of PVC. It does look like that vine is small for 10 years old.

I didn't want to use the fence because of the morning glory and everything else that keeps growing on it. Very annoying and I have to pull it clean all the time.

Also my neighbor's property drops a few feet from my ground level, so I could never go over and grab grapes from the other side. I saw a few tips and videos about a PVC frame trellis and I liked how inexpensive it was to make.

I might look for electrical conduit piping that I can fit over or inside the PVC pipe to create a new trellis.

Also, I cut everything off to try to get rid off the most I can of the blister mites. Id rather wait an extra year to be rid of them than to have them come back quickly. There is also plenty time left for the summer for it to grow some new vines, if its healthy enough?

Would anyone recommend I built something like this trellis and bury the pipes a foot into the ground to secure it?

https://www.simplifiedbuilding.com/projects/building-a-backyard-grape-vine-trellis-with-pipe-and-wire

looking sharp there guy (mine I painted green and go through concrete into the ground), the video is going into asphalt, you have grass, not quite the same as you drive and set up posts, if one post settles funny - the whole thing will look half ass, i would set the posts into sleeves which can be PVC (or cardboard for that matter)into the ground flush with the grass and pour concrete after everything is all set, a bag of $8 redimix will do