If the larvae are pinkish with dark heads, you've got iris borers. I can assure you they did NOT come from Suttons. Borers don't live in CA. They are a pest of the Midwest and East Coast.

Unfortunately, you have missed the opportunity to control borers chemically this year. It's already too late in the season. Chemicals must be applied very early in the spring before temps reach 70 degrees (borer hatching temp) in order to kill the new hatchlings. Once the larvae have hatched, fed, and grown larger, chemicals no longer kill them.

At this point, your best course of action is to kill them manually while they are still feeding inside the leaf fans. Start at the base of each leaf, running your fingers up the leaf, squeezing it between your thumb and fingers as you go. If there is a borer in the leaf, you should feel it pop when you squeeze it. As long as you kill the borer in the leaf, it'll never make it down to the rhizome where the real damage is done.

Good luck!

Laurie

I didn't mean to imply the pest came from there. I just love the company and think they have wonderful iris's.

What do I have to spray with for next year?

Imidacloprid is very effective against iris borer. It is marketed as a granular product for lawn grub control by several companies, as well as a wettable powder for spraying. I personally use the granular form. Just make sure the product you purchase contains only imidacloprid and no other ingredients. Apply early in the spring before temps reach 70 degrees, and water in well. One application lasts all season.

Laurie