Q.What causes the grapes to dry up and fall off the vine
The grapes on my muscadine grapevine, (Black James grape) fall off the vine when they are still very small. It seems like they just dry up and fall off. The vine is loaded with baby grapes but they do not reach maturity.
you have to polinate your vine when it starts flowering, thats what Mr Bee does, when he flys arround your garden.
I had the same problem, year after, i polinated the plant with a fine brush. ( Grapes plenty )..