Looks like some type of scorch. Don’t think that it is Pierce’s Disease.
If it is not widespread on the vines I would not be too concerned.
Phew! Yea it’s on about 10 leaves. It’s a second year grapevine. I was concerned about Pierce’s disease.
Did you fertilize the vine? If so, what did you use?
Also, any sprays? Sulphur can burn certain varieties.
I actually did not follow any recommendations for fertilization. I didn’t really fertilize it. There is a raised bed about 6 feet away from it that was headily amended with compost. And then recently after realizing that compost is insufficient fertilizer, my mom has been using Miracle Grow to fertilize the vegetables there. I think she may have used miracle grow on the grapevine itself as well.
This is the first year I really got into serious gardening. So I still have to research the proper fertilization of grapevines.