I am new to iris but DD moved some of hers here 5 years ago. They have been disappearing slowly ever since. I am not sure it isnt a combination of borers and rot.
ANYWAY!!
I use Bayer Tree and Shrub .It says "for borers" right on the lable. Its a liquid and I sprayed our iris last year. Many iris people use this . I will drench my new iris this week as its been in the 70's and will go to 80 a couple of days. I also use Bayer on my lilies for the Red Lily Beetle.
The product containes Imidicloprid which is a "soft skinned insectacide" guess thats the borer alright.
