Is it really that bad? Often clearing out the old foliage at the end of the year, and any you have now, will take care of it. Have you tried spraying with a fungicide? I remember reading somewhere that you should add a bit of dishwashing detergent to the fungicide to keep the solution on the leaves, iris are thicker, slick & it tends to slide off.
I've had a problem this year, & occasionally in the past. I have my iris too thick, & we've had lots, lots of rain this year. I've seen it other years when it has been really wet. I just cut out the dead leaves, & always cut them back in the fall. That seems to do it for me, but I would certainly use a fungicide rather than get rid of your beautiful iris. Might be a bit of work, I think you might need to reapply occasionally this year, but that should take care of it.

Not to worry, they may look awful now, but get all the leaves you can, spray with fungicide, etc. In the early spring, all beautiful new leaves will come up. Even if you still have leaf spot, it will not be evident at the start when they bloom, but will become more so toward the end of the season. Keep everything clear so they have good circulation.

You may not beat it if it's in your soil, but you can control it so you still have beautiful iris with decent foliage. Not perfect, but it is still worth having iris. Rotate your fungicides as always.

kay

Not too worry. I've had it rampant one year and none the next -- with NO spraying. Wasn't that rain amazing?! Everyone panics when they first experienced a bad year - it does no harm to the iris at all! Unsightly as all get out. I've had it in hot years. No rhyme or reason.

At the first sign of it you can spray with a rose fungicide or Daconil - this innoculates the unspotted area of the leaves. Repeat per directions.