Onion rust is a disease caused by the Puccini all fungus, the same rust fungi that attack roses.
How to control rust
To break the cycle of onion rust, rotate all Allium crops every 2 -3 years and discard any infected plant tissue. Other common Allium crops include leeks, scallions, and garlic. Avoid excessive irrigation and remove all dead or diseased plant material.
You can grow a surprising amount of food in your own yard. Ask me how!