Sorry, I have no first hand experience with this topic, however, you can google 'iris borer' and get tons of information. Here is one website that hopefully will help you: www.irisgarden.org/pesticides.html

Thank you. Ended up at Garden Shield. They have a product that I am going to try.

This time of year, borers can only be killed manually by digging the infected plants and cutting the borers out of the rzs. In very early spring, however, newly hatched borer larvae can be killed with imidacloprid. Imidacloprid is only affective against hatchlings. Once the borers have fed for a while and grown larger (as would be the case now), imidacloprid can no longer kill them.

Garden Shield will not kill borers. It might or might not repel borers from the plants, though I don't believe it would be effective in doing so once the borers are actually INSIDE the plants as they are now. Also, Garden Shield will leave the leaves on your irises badly spotted, and it requires reapplication after every rain or overhead watering.

Laurie

Thanks Laurie, So far that is what I have been doing. That is killing them manually. The Garden Shield was not a working website so that ended up with nothing anyway.
Now I know nothing about pesticides so does imicacloprid go by any other name?
I dug up one whole iris bed. Found 3 borers but tons of root rot but we have had a lot of rain the last 10 months.
I think the comet helped with that.
GraNeeP42

Imidacloprid is an ingredient in lawn/garden grub control. Check out the bags of grub control for their list of what's in it. Some have it, some don't.

Thanks everyone. Have been doing more research. Imidacloprid is the active ingredient in Merit by Bayer. Also have been researching grub killing nematodes. They would work now as they go into the soil. What I didn't want to know about just growing some pretty flowers!!! I found another borer tonight. He was outside of the root so must be ready to go into the next stage before the moth. Hope I get my nematodes soon. Thanks again.

I work at Presby Memorial Iris Gardens in Montclair, NJ. This is our third year using nematodes. We have very few borers this year. That's amazing considering that we have over 10,000 irises and found borers in less than a dozen plants! Most were in an area away from the display beds. These had not been treated before. The first year we still had some borers, the second year, even less. This year is the best. We were told it would take 3 years to eradicate them. Seems to be true. It's best not to plant irises near trees or tall shrubs as the moths stay in the trees and lay their eggs in that area. We are skeptical about using chemical pesticides as we have our honey bees in the garden. It's best to apply nematodes after it has rained. They like wet soil and wet leaves.

That's great news! What kind of nematodes are they?
Renee