Protect my grapes

Asked June 22, 2016, 12:36 PM EDT

I have Concord grape vines that have produced large crops over the years. Last year, the garden was overgrown and the grapes turned black and dropped off. The garden is cleaned out and I want to protect the grapes from fungus. The leaves look OK, but fruits are just starting to form. How do I prevent that this year? Is there a safe fungicide I can use? I removed wild grapes and greenbriar from a nearby hedge. Wineberries look healthy so far, as do elderberries. Blackberries may or may not be OK, can't tell yet. Figs need weeding. Help my Concord grapes, please!

Cecil County Maryland grapes fruit concord grapes grape black rot

1 Response

You must have wonderful vines to escaped for years without fungal problems! Now that you have cleared up around your vines, which improves air circulation and quicker drying of the leaves, perhaps you will not have a repeat of your black rot problem this year. This fungus is a common problem and hopefully you can prevent it from becoming established in your vineyard.

In order to prevent black rot, gardeners spray beginning when the new shoots are starting in the spring. First when they are 1" long, then again 7 day later or when they are 4" long (whichever is earlier.)
Sprays continue every 7 to 10 days, depending upon moisture (rain) pressure.

We primarily recommend Immunox or Mancozeb fungicides.

You may be able to minimize spray in dry years or dry springs. But there are also cultural steps to take to prevent black rot. One, of course, is to improve air circulation.
Also, this fungus overwinters in the mummified berries from the previous season. Spores are released during wet periods before bloom, when new shoots first emerge. Young leaves are infected first with tiny, black, pimple-like spots that produce more spores, which then infect the fruit. Fruit is susceptible until just before ripening, when berry color is developing. As the skin thickens with ripening, the fruit is much less vulnerable. So, remove all old dried berries.

Besides improving air flow in general, you can also prune out leaves around each fruit cluster to improve air circulation.

Virginia creeper, a native vine, also can carry black rot disease, so remove any of these that are nearby.