Black rot kills grapes

Q. My grapes turn black before I can pick them. How do I prevent this? Can I spray the ground? How can I grow perfect grapes?

Pauline, North Lima

A. Grape production is not as easy as most might think. But it can be accomplished. Many backyard gardeners such as Pauline enjoy making juice, jelly and other goodies from their grapes.

That is, until black rot finds their vineyard. This disease is the most-common and most-destructive disease on grapes. Just before harvest, the grapes turn dark, shrivel up like raisins and finally get white/gray dots on the surface.

There are early warning signs if one pays attention early in the season. The disease persists on plant debris left behind from last year. Once spring arrives, the fungal spores can be carried by raindrops back onto the emerging shoots of the grapevine. Early signals of problems will be orange to yellow spots on the leaves.

I never recommend spraying as the first choice when trying to prevent or reduce diseases.

Here are some tips for prevention:

Choose a better site: Grapes need wide open spaces with lots of sunshine. If your grapes are growing in any shade, they need to be moved. Proper air circulation is vital. Well-drained soil is important as well.

Use a proper trellis: A grape arbor should not be over your head. It should be in a straight line and only 5 feet off the ground with two wires — one at 36 inches from the ground and one 24 inches above that.

Clean: Each fall, all fruit, leaves and other debris from grapes should be removed from the area. Fungal diseases survive on this plant debris. Removing it reduces the chances of infection for the next year.

Prune: Most gardeners are shocked at how much grapes are pruned back. Know that grapes are produced only on 1-year-old canes. Thus, what produced fruit last year will not fruit again. When leaves emerge, there should be only 8-10 buds (emerging shoots) per cane.

Scout and observe: Starting with the first bud break in early spring, take just a couple of minutes each week to check on the grapes. Prune back wild growth to improve air circulation. Watch for signs of disease and prune out infected leaves.

For more details and information on preventing this disease in 2015, go to: http://go.osu.edu/growgoodgrapes.

Eric Barrett is OSU Extension educator for agriculture and natural resources in Mahoning County. Call the office hot line at 330-533-5538 to submit your questions. Clinic hours vary this time of year due to the winter season.