Peppermint rust
How to get rid of the fungus
From the end of April to mid-May there are tiny black dots, which become purple, then yellow swellings. In summer there are orange-brown spore deposits on the underside of the leaves.
Abhilfe
Radical pruning helps against peppermint rust. The plant should then sprout healthily again.
Jerzy Opioła, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons
