Iris rhizomes eaten! - help!

While weeding my garden today I noticed that several of my irises looked poorly. Upon closer inspection, the rhizomes were literally eaten hollow. What kind of critter will do that?
I dug them up and dusted them with Sevin (since it was all I had on hand) to be safe before replanting them.
Any advice is welcome!
Thank you!

Probably Iris Borers. Here is some info on how to deal with them Sorry that happened. I would hate to lose any of mine.

http://www.extension.umn.edu/yardandgarden/ygbriefs/e122irisborer.html

This message was edited Oct 12, 2011 10:21 PM

I found a pupae shell while weeding. I shall have to keep a watch on that bed in the spring.

Keep us posted on what happens.

Thank you, Kwanjin, for the informative link. I haven't seen a lot of the damage described. There were worms and grubs in the rhizomes when I lifted them out of the ground. Will white grubs (presumably japanese beetle grubs or something like them) eat rhizomes?
I haven't seen any pupae shells and I was doing a lot of weeding!

Two years ago moles or voles ate my lilies and some of my iris. They hollowed them out. My neighbors cat became very friendly with me. I started to give it just a little cat food so it would stay around. He started killing them. Sometimes he even wanted me to eat part of them. lol.

Don

I have a couple irises in one bed that I think might have been vole-eaten over the summer... I tried to get a division for a friend and discovered the rhizomes looked fine on the top, but the lower surface had been chewed (like eating a carrot sideways) until there was very little left of the rhizome. No sign of borers (foliage looked fine in spring, no pupae or shells found), and it just didn't look like the borer damage photo I've seen (also counting on the imidacloprid I put down in spring to help with prevention).

So, I'm glad I don't think it's borers, but I'm sad because I'm not sure the iris will come back. They can be pretty tough, so my fingers are crossed! I did lose a lot earlier this summer and more this fall with excessive rain... they just rotted. Interestingly, the ones whose rhizomes are planted (against "best practices") slightly below the surface and even mulched in some beds seem to have done all right. Could be that drainage is just better in those beds.

I have struggled to grow bearded iris up here and tried most everything. Cover, no cover, dirt, leaves, etc. I uncover them in the spring asap. I am now beginning to think that a light dirt cover and leave them alone in the spring is the key. as you noticed, against all advice, the ones with a bit of dirt cover seem to be the ones that survive. I am beginning to think that by uncovering them too early in spring to avoid rot, I was allowing them to freeze. So this year I have several that have survived and I am leaving them alone. I planted a few new ones and lightly covered. I will leave them alone come spring also. Perhaps I have found the answer. I had three bloom this summer, the very tall ones, while in the last year or so, only the dwarves seemed to survive. Thought it might have something to do with the corm size, but I don't think so. time will tell. I am, if nothing else, persistent. I just can't afford to do it on the same scale I used to while working.