I live in northern NY and have lots of grapevines. In June the vines are loaded with grapes.?

Plant Mint under them. This sounds like mites, Possibly ants, or Beatles. And some spray. Buy a 10x jewelers lens, or pocket microscope. For inspections. Of the grapes. Once mint is established. Go out and crush a few leaves every day. Effective as calenthrol oil. And natural. Some use garlic,or wild onions under the vines. Some thing is biting through the grape skin. Letting them dry. Weather check variety of grapes. To make sure they can grow there now. Global warming. Many grapes are having to be moved. And other varieties planted. But this usually don't dry them all. Slower there. I have grapes in IL. I use to never spray. Now every June. Beatles come from some were. And lay eggs on the vines. Then hatch. Why you need a 10x to see this.

sounds like a disease has hit your vines..... read here

http://www.ca.uky.edu/agcollege/plantpathology/ext...

I'd also suggest you get in touch with your Extension Service office in your County and see what help they might offer you.... some of these diseases can be spread to others and can ruin companies like Welches or wine makers... they'll appreciate you getting a handle on this.....

here's how to contact them.... clik your state, then your county....

http://www.csrees.usda.gov/Extension/