How awful. I've read that squeezing the leaves kills those hidden ones.

I hate those things. I had an infestation 2 years ago. I dug out my iris tubers and soaked them in a 10:1 ratio of water to bleach. Dug out and killed as many of the borers as possible. Cut out the squishy parts of the irises. Then replanted. I haven't had an issue with them since.

When I had them, after cutting out the gooky parts I was told to drop the rhizomes in bleach water for a few minutes. Soaked them 5 mins, rinsed them off, dried them and re-planted. They went on like gangbusters for years. There is an antibiotic (very pricey) they say to use in the soil to kill and residuals, but I never used it, I just removed the soil about 3" down and planted them in new soil I added.

So, even though they are fully leafed-out, going into the heavy growing season of summer, I need to cut back all the leaves on each plant to 5-6 inches and dig them up and soak them? Will this harm the rhizomes?

Before you start digging up and soaking, I would recommend going over to Facebook Iris Lovers and Iris Addicts Anonymous.... there has been alot of talk there about dealing with borers.. I know soaking in bleach water was not a recommended way to deal with them.. Honestly I didnt much more attention than that, because I am blessed enough to live in an area that dont have borers..

Hmmm...I searched Facebook and the Iris Lovers page wasn't available and no Iris Addicts Anonymous was there.

I did buy some Grub, Worm & Borer Killer (Spinosad) spray yesterday and was thinking this might work. The lady I bought them from mentioned this.

Here is the link for IL https://www.facebook.com/groups/irislovers/?fref=nf Let me know if this doesn't work for you..

Thanks littlebit, I joined the group!

It's just as I thought, spraying when the borers are in the leaves/rhizomes at this point in the season is a waste of time. I've done a pretty good job at hunting out the existing borers so far.

Looks like all I need to do at this point is dig them up, soak clean, and replant. Ugh! Next year I will be ready and will put down grub control granules in the spring as well as do a thorough cleanup in the fall.

Years ago I guessed that some really old varieties like the sans souci/honorabile group (which are really my favorites anyway) were more resistant to borers and that seemed to hold until I got distracted for a couple of years and lost all my Germans and some other favorites during some really hard to garden years. The Siberians survived just fine, and there are ignored but massive patches of Germans around the neighborhood now and in full bloom; so I sorta doubt the resident borer population around here is very significant. I think I will try some of the real old heritage varieties again.

I really don't think the grub control granules will do much good for you. This is not an animal that spends time in the soil (which is what those granules are for). The eggs are laid on leaf tips and on iris leaf debris in late summer. This is why it is important to clean up all that debris and trim leaves in the fall, once all egg laying is done. The eggs then hatch once temps get up in the 70's, bore into leaves (above ground), and work their way down inside the leaf until it gets to the rhizome. Please avoid using any systemic insecticide (commonly available Bayer products, among others) if you care anything about bees (these are flowering plants), and realize they will be taken in by other garden plants as well, some of which you may want to eat. There is good research that completely non-toxic parasitic nematodes are more effective against iris borers (http://www.irisgarden.org/borermain.html) so why use something so damaging as the sytemics. I'm not even one of the nutso completely organic, anti-pesticide completely, kind of people, but I do believe we should pay attention - although I want to completely kill the iris borers, I really don't want to be harming something so vitally important as all the various native pollinators as well as honey bees.