Iris borers are a problem that we all have to deal with. I dig up the iris tubers and clean them up as you did then soak them for about an hour in a 10% bleach solution and replant them the following day.

I am not sure where the idea that a bleach solution would control an insect larva but it does not, except maybe to drown them in which case just leaving the Iris rhizomes in a tub of water for an hour would work just as well. The Bleach solution is to control the soft rot that can follow an infestation of the Iris borer, but not to control the borer.
Understanding a bit about the borer is necesary before control can be achieved. A moth lays the egg that hatches into the borer and after hatching the larva tunnel into the leaves eventually working down to the rhizome where they mature and then leave to enter the soil where they pupate. If you can remove the part of the rhizome the larva is in and have a good healthy chunk of rhizome left to plant nothing more needs to be done, except to be sure that soil has no pupating borers that will, next spring, emerge as Moths and lay eggs on your Iris again. If good helathy rhizomes are not available and you will be replanting rhizomes that did have a borer (now killed hopefully) in it you may want to dust them with sulfur as a fungicide, but not bleach.

What interesting information from kimmsr! I hated the idea of dealing with a large amount of bleach. I've just found borers in each of my beds.

Something weird: when I entered iris borer in the search box on this forum and on the iris forum, I kept getting a message that the server had dropped the connection. But when I entered borer, I got all the threads that mentioned iris borer. Strange, huh?