Avatar for dawilliams69
Jul 27, 2017 6:06 PM CST
Pittsburgh, PA
I have two catawba grape vines. They are about 5 years old. They have spread out a great deal and look very healthy. Every year I prune them in the recommended fashion. Each year they produce about 1,000-2,000 green grapes. My problem is, every year, the grapes go from green to rotten without ever ripening. Does anyone know what causes this and/or what can be done to prevent it? Thanks, Doug (Pittsburgh, PA)
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Jul 27, 2017 6:12 PM CST
Name: Karen
New Mexico (Zone 8a)
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Welcome to NGA! I can't help, but maybe this member will have an answer for you: @ediblelandscapingsc.
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Jul 27, 2017 6:17 PM CST
Name: Daisy I
Reno, Nv (Zone 6b)
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Summer Bunch Rot?
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Jul 27, 2017 7:49 PM CST
Name: Daniel Erdy
Catawba SC (Zone 7b)
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Thanks Karen, my guess would be grape black rot because you said they go from green to rotten before ever ripening. Summer Bunch Rot will only appear when sugars are above 8% and the grapes start ripening. The timing is right for black rot to start showing up, it likes it hot and humid. Frequent rains and temperatures in the high 80s are perfect for black rot infection. Black rot affects all parts of the plant, but the most damaging effect is to the fruit. Most infections start when the fruit is half to almost full size. Early varieties with large grapes are the most susceptible. In general, grapes that ripen late in the season are affected the least.
Black rot spores love moisture, so you want to reduce the amount of moisture held in the canopy by providing great air circulation. During dormancy, prune heavily keeping only a few healthy, strong canes from last year's growth to allow better air to flow. Prune out any diseased parts of the vine and keep the vine tied up and off the ground. If all else fails there is also numerous fungicides you can use if you want to go that route. Good luck and please keep us updated.
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Avatar for dawilliams69
Jul 27, 2017 8:47 PM CST
Pittsburgh, PA
Thank you Dan and all who replied. It may be too late for this year's crop but I'll give it a try. At least next year I'll know what I'm facing and I can take steps earlier in the season to prevent it. Thanks again!
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Jul 27, 2017 8:52 PM CST
Name: Karen
New Mexico (Zone 8a)
Region: New Mexico Region: Arizona Region: Ukraine Cactus and Succulents Plant Identifier Plays in the sandbox
Greenhouse Bromeliad Adeniums Morning Glories Avid Green Pages Reviewer Brugmansias
I'm glad you got the problem identified. Thank you, Daniel! Good luck, I hope you can have a nice crop next year.
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