grapes--what makes them fall off when they are tiny?

[S.Hearn]

Any update on this. I am having the exact same problem. I have green grape and I too forgot the name. I am in North Houston area and bought the grapes at Walmart which likely was not a smart move. Beautiful bunches, loaded with pin head size grapes, then they all start disappearing leaving a empty vine bundle skeleton that eventually shrivels. Leaves look good, no insects seen, so I am curious if birds are stripping them?

I have the exact same problem with my muscadine grape vine dropping forming grapes this past spring.. now I have some sort of green fly attaching and dying on the vine. The leaves are showing brown spots and deformation on new leaves. My muscadine is cowart variety and self pollinating. Never knew this grape growing was so difficult. I'm in deep admiration of those successfully growing their own. I have a red variety (don't remember which), cowart muscadine, and 2 seedless concord grape.