I don't know whats happening there. Those grapes do look like females and not some wild grape. Different varieties do take different numbers of years to come into fruiting, but this far apart seems like a stretch. There is a small chance there could be a nutrient deficiency of e.g. Boron. I would throw on some micronutrient fertilizer like Plant Tone to coverer that case. Also make sure not to over fertilize, some varieties respond to that with nothing but growth. I don't think you have a disease there, the plants look healthy. One other possibility is the variety is some official grape variety but not Fredonia, and it is one that needs pollination. Very few grape varieties need pollination and your Concord should be giving it, so this is a remote possibility. I would give it a few cups Plant tone or similar for the next few years and otherwise not fertilize. If it doesn't fruit in two more years, pull it out. Let us know what fertilizer and how much you have been giving it, to see if it sounds like too much. Scott

Probably grape phylloxra. Link to pictures: https://www.google.com/search?q=grape+phylloxera+pictures&client=firefox&hs=BVB&rls=com.yahoo:en-US:official&tbm=isch&tbo=u&source=univ&sa=X&ei=yiuqUZLtNsXT0wGSkoGYCw&ved=0CDIQsAQ&biw=1280&bih=610 Here is a link that might be useful: grape phylloxera management This post was edited by fruitnut on Sat, Jun 1, 13 at 13:22

That is black rot. It takes over grapes in many parts of the US after 3-5 years so it fits your situation exactly. There are several sprays that are effective on it. For organic growing about all that works is copper. If you are not organic you can use Immunox or mancozeb. Even though some things will work on it, the majority of the disease sprays will do little or nothing so you need to spray something that is known to work for it. Scott

It may be that the grape is marginal to your zone (4-4B is pretty far north for most grapes), and the added stress of competetion is causing hers to die back. It could also be that yours is in a slightly warmer microclimate and allows it to thrive. Either way, I agree with you, one plant per hole.