Concord Grapes Turning Brown

alphonse55July 13, 2009

I moved into a house in October that came with a good size concord grape vine. I didn't really do anything with it as I had so many other projects to work on. For a while it seemed like it was growing well and I had a bunch of little green grapes. A few weeks ago all of them started getting brown spots and eventually just turning brown. I was thinking maybe it was a result of the huge amounts of rain we have had but I really don't know. I now realize that I should have done some heavy pruning before spring but pruning aside is this something that I can avoid next year or have the heavy rains not been good for my grapes?

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jean001(z8aPortland, OR)

They could be sunburned. But that said, you don't say where they are brown.

Can you post pictures?

    Bookmark   July 13, 2009 at 5:28PM
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alan haigh

Probably bunch rot. A single spray of immunox the first week of June would probably lead to a huge crop of grapes- otherwise everything rots.

    Bookmark   July 13, 2009 at 5:53PM
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my grapes would rot every year until someone told me to use immunox which i did for the first time this year. its working a treat. no infection at all, though ive been spraying every 2 weeks pretty mucn since the leaves came out. my grapes r now about 2/3 developed and i sprayed them on sunday and probably will not spray them anymore this year. i will cut back on the spraying next year as hopefully, ive wiped out most of the overwintering spores.

    Bookmark   July 13, 2009 at 6:10PM
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jean001(z8aPortland, OR)

Maybe so. But we still don't know where they're brown.

Can you post a picture?

    Bookmark   July 14, 2009 at 12:27AM
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alan haigh

The reason we're so confident about the bunch rot diagnosis(although with so little info mistakes are always possible) is that it is extremely common in the humid east. It starts with black spots on the tiney grapes and leads to completely rotten bunches before grapes can ripen. Seedless grapes are almost impossible to grow here without its control and Concords often succumb- especially during wet years. Once the innoculum is there, intervention will probably be necessary, at least for the following season.

Lychee, the only way to find out how little spray you can get away with is to take a chance. I gurantee you that if you stop spraying now your grapes will be fine. The rot has to get a foothold while the grapes are very small for some reason. A single spray may be risky, although I've had good luck with it but 2 or 3 sprays the last week of May into June has never failed me. I consider Concord to be less susceptible than most varieties I manage.

    Bookmark   July 14, 2009 at 5:57AM
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Sounds like black rot to me. The berries turn brown and start to shrivel-the black refers to the tiny fungal bodies and not the color of the grapes. Bunch rot (Botrytis) affects ripening berries (which will turn fuzzy), while black rot infection strikes early. Once the berries get near veraison (change color) and the sugars get above ~5-6 brix, they become resistant to black rot infection.

    Bookmark   July 14, 2009 at 10:36AM
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Scott F Smith(6B/7A MD)

I agree with kiwinut, the most likely thing is black rot. I expect that is what harvestman may mean by bunch rot. Concord is highly susceptible to black rot.


    Bookmark   July 14, 2009 at 11:00AM
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alan haigh

Bunch-rot- black rot- you're probably right. I may have confused the name but what's is important is I know the treatment. It works so well, I haven't looked it up for about 10 years. I took the chance to find out how little I could spray to control it and now I can save you guys a lot of trouble. Of course, further south you'll have to tinker a bit. Kiwinuts research based info does not jive with my experience. My hunch is that myclobutanyl (Immunox) just knocks the innoculum out of town when you apply it early because I don't keep plants sprayed nearly as long as that info would suggest would be necessary.

    Bookmark   July 14, 2009 at 7:49PM
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