Grapes grown in a glasshouse in Cheshire England

Question

I have tiny dark spots on my unripened grapes. These look nothing like the spilled ink effect which illustrates the suggestion of sooty mould. They are relatively few in number and appear randomly on the grape. They can be scraped off with a fingernail and can also be washed off.
Sorry, I do not have the technical know how to send you a photograph. What is causing them? Are they harmful? If harmful, do you have a suggested cure?

Best wishes,
Stephen Fuller

Answer 1

Have a look at this article could it be black rot?
https://www.gardeningknowhow.com/edible/fruits/grapes/black-rot-grape-treatment.htm