Grape black rot

I have been trying to fight black rot in grapes, Guignardia bidwellii organically.
Quote from wikipedia, "Black rot is probably the “Achilles heel” for organic grape production in the East."
Cultural control practices didn't do much. Sanitized everything, even changes the ties. Organic approved sprays including copper seemed to provide very short term improvement (i.e. black rot started a little later). All mummies were cleaned up. The loss was 90% of grapes last year. The birds got the rest.

I don't know what varieties we have (there are 2) as the old owner planted them. He also sprayed, I am pretty sure. The grapes actually did great for 2 years after we inherited the vines (without spraying), but since then black rot has been here to stay.

Should I start over with new resistant varieties? Does anyone grow any actual resistant ones in area that is prone to fungal disease?

That sounds like it is caused by a fungus.  Have your tried a fungicide?

This thread has several simple recipes that would be cheap and easy to try:

https://permies.com/t/93537/toxic-Fungicide

I do not have any experience with that particular disease.

It may take several spraying to get it.