I had one cultivar two years ago that looked like it had scorch. I dug it up and discarded it. I replanted a new iris in the same spot later that summer. The new iris has done well. I had no others like it, so if it was that, I think I got it in time to keep it from spreading by insects to other plants. They seem to think it needs an alternate host to spread.
I had one last year with a bad case of rot. I dug it up, cut out the bad rhizomes, soaked it in bleach water, and left it dry out for a few weeks, then replanted it in the same spot without treating the soil. It grew back, and it seems good this spring. Nothing near it was affected.
