I did this around the start of July and have had about half of them take. That's much better than past efforts which are well under 5%.
Today I did a few more of the green-on-green cleft grafts. One thing I'm noticing is that it is hard to graft over some of my vines, as they get tangled growth and I have trouble removing the host and not the scion growth. When pruning today, I accidentally removed several feet of growth from one of the 3 success I had last year.
So, I decided to take a more agressive approach to removing the host vine's growth. Here's a Neptune which I decided to graft over.
All the grapes rotted last year (black rot, I think) and most of them did this year as well. This is in spite of fungicide treatments which seem to have worked for most of the other grapes. These two clusters are 70% of what is left on the vine. I decided that they weren't worth bringing to maturity...
Neptune to start with:
A drastic Cut:
I'm not sure if a summer bark graft will work. I haven't tried them before, but it's worth a shot. The tape is vinyl and I put it sticky side out, as I wasn't able to find my roll of rubber Temflex.
I'm not all that confident in the bark graft taking, so I added a green-on-green cleft graft (the thing I've started having success with) on the side-shoot just under the bark graft.