Fungus on grape berries

Asked August 10, 2017, 8:08 AM EDT

I have a huge purple grapevine which produces quite a bit of fruit but it gets a fungus every year. I don't want to spray a pesticide. I tried sulfur this year but I think I started too late . What can I do ?

Ingham County Michigan

1 Response

I am guessing the grape you have in Concord and the fruit rot is black rot. Concord is very susceptible to black rot. Here is some information on black rot.
Black rot is very easy to control but sulfur does not work well against the disease and Concord grapes are sensitive to sulfur so they should not be sprayed with sulfur after they leaf out. Pruning the grape vine to open the canopy will help and a dormant spray of sulfur early in the spring will help. Be sure to remove any mummies from the vine. Black rot can be control with a few sprays after bloom as that is when the fruit is susceptible to infection. Captan is available and pretty safe a spray at the end of bloom and another 2 weeks later should control the disease. If there is a lot of rain you should shorten the interval between sprays but the berries should be resistant to infection about 3 to 5 week after boom. Some of the Bacillus biological pesticides also give fair control. They are considered organic you should look for the trade name Serenade or Sonata or the active ingredient Bacillus subtiis.