Grape affliction

Asked July 7, 2018, 1:29 PM EDT

My uncle's grapes (concord I think), developed some sort of discolor and some became desiccated over the weekend (June 29 - July 2, it was the hot one if you remember).

Did some research online, and it appears that it was some kind of fungus, although I am unsure which type.

My question is, can you identify the type of ailment from my attached photo, and recommend a remedy?

Some background info: the vines are located in Bridgman, which I believe to be concord, though I am not certain. The symptoms appeared over a weekend, which was particularly hot and humid- a factor with certain fungi from what I read, and roughly half of his current grapes seem to be affected, and the leaves appear to be not as widely affected.

Berrien County Michigan

1 Response

I assumed it was black rot before I saw the picture.
The fruit is not quite in focus.
I wonder if it is anthracnose. Concord is supposed to be resistant.
Here are some links to those two diseases.
Grapes are very susceptible to fruit diseases at and after bloom and the fruit should be protected. The fungicide captan is effective against both diseases.
You should spray with a fungicide if it rains during bloom. Spray every 7 to 10 days for the 4 to 6 weeks after bloom. Spray more often if it is rainy and less often if it is dry.
Wet conditions are necessary for infection.
You are at the end of this import spray season so I would suggest you spray. You will not be able to save the infected fruit but you will be protecting the remaining fruit.

Here is the black rot model for grapes with the weather data from Scottdale.
You can see there were some significant infections during our abundant spring rains.