Sometimes we get really good questions via Facebook. 

Jessica has a problem with black rot on a grape plant, and is looking for a home remedy as she would like to avoid chemicals if possible.

We reached out to Emily Tepe from the University of Minnesota Department of Horticultural Science, and author of The Edible Landscape, to help Jessica solve the problem.

Her advice:

The best thing you can do to control black rot on grapes doesn’t involve chemicals at all.

The first, and most effective practice, is good sanitation. As soon as you see any sign of black rot on any part of the plant, get it out of there. Clean up any berries, leaves, and pruning’s from under the vine and keep it spotless and weed-free all year. The fungus overwinters in this kind of debris and will wreak havoc as soon as spring rains come.

This leads me to tactic number two: good air circulation. 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. Prune out any diseased parts of the vine too. Keep the vine tied up to a trellis to allow air to flow through. 

Another good practice is cultivating the soil under the vine shortly before bud-break in the spring. This can bury spores, thus preventing them from reaching the plant. This has proven quite successful for many growers. 

As far as home remedies go, I’ve never tried any on grapes. You could certainly try them, but here’s a thought: Most home remedies involve a water-based solution being sprayed on the plant. This doesn’t sound too good to me, considering how much this fungus likes moisture. 

Chemical sprays are effective, but have to be applied numerous times throughout the season at very specific intervals. Every inch of the plant has to be covered to be effective. That’s a lot of work and a lot of exposure to some nasty stuff. I suggest diligently following a good sanitation, pruning, and air circulation routine. That usually does the trick.

Good luck Jessica, and anyone else who has this problem!

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