Harley, You are probably too late to treat them now, You could salvage some of the firm rhizomes after you check to make sure there are no borers in there. It's important to discard, as in burn or put in the trash the old leaves and infested rhizomes. After you re-plant, you may want to treat the new irises with a systemic product that kills them. I use a product by Beyer that is used to kill grubs in your lawns. You need to treat the areas where you are growing iris in the spring after you have a streach of weather above freezing for about 5 or 6 days. That's about April in my zone. Then each fall and spring, you will want to remove all of the dead leaves and burn or discard them, don't put them in the compost, as that's were the new crop of borers eggs are. Even with treatment, you may find one once in a while. Good luck!
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