Discouraging amount of work

I went out to check on my theory this morning, and The dense patch of iris/asparagus has no noticeable iris borer damage, except for one at the very edge of the patch. That whole patch has not been touched for at least 5 years. except to harvest the asparagus and put the weeds that grow between. This is a patch of the old grape kool-aid irises. I thought maybe it was just the flavor that the borer doesn't like, but there is a patch of the same iris that I just moved last year to a new spot, and I see the signs of borer damage already in that patch.

I think I will experiment with growing some of my newer TB's with asparagus. I wonder how long the borer will hang around if it didn't have any irises to eat.
Will it choose another host?

I give! I think I will probably go with the merit next spring. I am still going to have to lift and inspect, bleach and replant everything, but I will have to replant in the same ground as I don't have the energy to dig huge new beds. Most of the borers I am finding are in the rhizomes with the icky slimy center leaves near the bottom of the rhizome. I am just throwing these away (dumpster ok?) unless there are no good rhizomes of that variety left. Then I will try the surgery route. Thanks for the support and encouragement, it has really gotten me down the last few days.