Q: What’s wring with my grapes? This is the second year in a row. They get about 1/4 inch in diameter, turn black and fall off.
A: Your grapes have a disease called black rot. Its first symptom is small yellow spots on the leaves. The spots shed spores which infect the fruit. Unfortunately, the fruit doesn’t show much damage until it is half mature…too late to prevent further damage.
You can slow the spread of the disease by destroying all infected fruit as they are seen. Rake fallen leaves in the fall and remove them from your property.
To really have a chance at harvesting grapes, though, you’ll need to begin an insect and disease spray program.
The University of Georgia has an excellent guide to fruit spraying:
Black rot on bunch grapes