Actually, I suspect it's powdery mildew or downy mildew. Black rot is just that, the entire fruit rots, dies, and shrivels away, often falling off. With the mildews, the skin is affected, but continues to live, with large gray-brown patches -- it can cover the entire grape, or only one side or part of it. The fruit under the skin continues to develop normally, but obviously, not good to eat like that. Any of the fungicides mentioned above will work. Another good one is Bayleton. I don't know if it's technically labeled from grapes. I bought 3 quarts of it in ready to spray, hose end type sprayers on clearance at Lowe's last year in the spring for $1.25 a bottle. It was sold and labeled as "Lawn Disease Control," but I used it on summer and winter squash, tomatoes, grapes, peaches, and also on my lilacs, phlox, and monarada, and it did an absolutely fantastic job of keeping them clean and green all summer, no disease problems at all. If I ever found more of it at that price, I'd snatch it up in a minute.

Yeshwant, It appears that you and Scott are talking about blackrot, something I have not seen on the west coast. All my grape ever got was mildew, so I took it out. Maybe if your neighbor read the fact sheet below, he would be agreeable to removing his vine, and installing a much better grape? You could make a rooted cutting off your plant and give it to him, costing you nothing really. I would advise you to check with several good quality local nurseries, (or the county/state ag service, but maybe they have no such options in NYC!) to see what all other kinds of grapes are resistant to disease in your area. See if Reliance is one of them. It sure is a good tasting grape and never fails to yield a ton of fruit for me. Comes from the same breeding program as Jupiter, in Arkansas. If you feel real adventurous, you could start grafting his vine over to a good grape, starting now, and eventually make use of his entire underground root system, which is a shame to waste. But it takes diligence to convert a vine over. I know, I have done it. You would need to cut a vertical slit in the mother vine (his) and insert a sharpened piece of current season's grape cutting. Bind up and seal the wound etc to keep air and water out. It would have a good chance of growing out next spring. Once that occurs, you can start chopping back the upper portion of the plant that is useless until all you have left is the desirable scion growing from the old stump. Here is a link that might be useful: fact sheet on blackrot

It was just a different world then, Jerseytom. About a month and a half ago I had a most interesting conversation with a third generation grape farmer and vintner, whose new house I was working in the middle of a vineyard west of Lodi Ca (wine capital of the world?). Note that Lodi has shut down several municipal wells due to toxic levels of pesticide in the groundwater. I camp out in a trailer on my jobsites, many of which are commercial orchards and vineyards, so I see what's going on 24/5. Generally, cherries and grapes are sprayed with something at least once a week ( often only 2-4 days) from March through October. Sprays include pesticides, herbicides, mildewcides, growth hormones, bud-break stimulators, etc. Chemicals range from the benign (sulfur dust compounds) to extremely toxic miticides (Omite). Needless to say, I no longer buy much produce. Back to the conversation between carpenter and farmer. C- You sure waited long enough to harvest those grapes. F- Yeh, this is the last day the winery is open. Next year they won't even take them at all. C- What variety are they? F- Kerrigans. The winery uses them to blend. C- So are you going to rip them out? F- Nah, We're going to bottle them under our own label. Those vines have been there a hundred years. This was the third vineyard ever planted in Lodi. C- A hundred years! I didn't know grapes lived that long! F- Those grapes will never die, well they'll go for at least another hundred anyway. ( On walks through the ancient head trained vineyard, I had found no vines of lesser maturity and no blank spots in spacing- zero disease loss in 100 years). C- Hey, how do you water them anyway, there's no water system. F- They didn't even have irrigation around here, back then. The roots go down 30 feet! I watered 'em once just for the heck of it. C- I never saw you spray, don't you even sulphur them? F- Are you kidding me, nothing bothers those Kerrigans. Why do you think I built my house in the middle of this vineyard? I could be happy living here forever. C- So does the wine taste cr@#$%? They sure look really productive. F- The wine tastes fine. This is some of the most productive land I've got. C- Are you going to sell the wine as organic? F- Nah, too much trouble. We're gonna sell it as natural. A little internet research reveals that Kerrigan is really Cargane, currently the most widely grown variety in France. Yes, I've bought a bottle of decent wine at a small grocery in France for a buck and a half, and wondered, how do they do it? (everything else costs about triple). Try finding Cargane in any list of varieties anywhere- UC Davis , L. Rombough, internet, etc. Not seeing them being sprayed, I ate them for several months. Purple, mild flavor, seedy, tightly bunched. I can't quite recommend them for table grapes, but you get the idea. The US had a great wine industry based in New York made from v. labrusca grapes until consumers were convinced they had have the latest high maintainance variety. There are wild grapes growing virtually everywhere in the US that could be used to develop disease free table and wine grapes grown locally. Maybe the rise in demand for local and organic will spur that development. Until then v. labrusca grapes (Jupiter, Glenora, Steuben, Alwood, Reliance, etc) are a good place to start in temperate climates.

Of course. And they make good juice too. The deal with those is that they have thicker skins than something like say, merlot, and when you make wine from them, it is rather tannic. But for eating, all the wine grapes are just fine. In fact, I think they are much much better because most "table" grapes are way too sweet for me.