I have to agree with Katherine, I have had a borer infestation, and it didn't look at all like this. They seem to ususally chew their way down the center of the leaves to the rhizomes, and when you dig them you will see the whiteish worm/larvae. I have no idea what's eating your irises, but you might want to consider using a systemic insecticide. I know it's supposed to be the year of the cicada, but since I have no experience with them, I don't know if they would do this type of damage. You might take some to your county agent, or perhaps you have a University near by that might help you.
