If you’re like me and you don’t notice iris borer until mid-summer, you have more work on your hands. If you are seeing yellowed leaves and rot at the base of the iris stalk, you have to dig up the plants to inspect them. Knock off all of the dirt. Cut away rotten parts with a sharp knife (and remember to throw these in the garbage). Place the remaining rhizomes in a bucket of water that is 9 parts water and one part bleach. Let the plants soak for 5 to 10 minutes. The borers will drown.