I use copper for fungal disease and yes, it is considered organic in it's more basic forms I like [url=https://www.biconet.com/disease/copperSoapFungicide.html]copper soaps[/url], or copper octoanate; there are a bunch out there...
The whole of genus Prunus is fungal prone, so to do cherries is to require a strong back-up and copper has been mine. It helped me stave off a number of fungal issues this year that I could not manage with biologicals alone.
That said, for low level fungii like mildews I find milk and water to be most effective (1:3). Neem can be useful on fungus as well, and I always have some around. Copper is a fall-back for me after I have tried less harsh methods; heavy metals should always be used as little as possible to avoid build-ups (hurting the active fungal side of your soil).