Some people treat the soil with various substances, but frankly I think it's a waste of time and money. Erwinia bacteria seems to be endemic in most soils, so treating your soil is only going to be a temporary fix at best before the bacteria repopulate your soil.

Just make sure you allow your rhizomes to dry for several days to a week before replanting to give the wounds time to scab over. Fresh wounds in the rhizomes will invite reinfection.

Laurie

Its more important to find a place for the iris which has good drainage. I think rot happens when water lays on the rhizomes for too long a time.
Laetitia