Sharing knowledge here:
Since I live in the San Francisco Fog Belt, I suffer from a variety of soil-borne funguses, including mint rust. In fact, mint rust is so severe that in the past I've had to rip out my mint every year and replant it from scratch in sterile soil and containers.
I've tried copper-based fungicides, but (a) they don't work very well and (b) they're toxic so not good for a culinary herb like mint. What can I do?