"The only real mysteries are that the borers don't seem to bother the Iris species that were native to the Gulf Coast (the "Louisiana Irises"
Actually, yes they do, at least here where they are transplanted into Maryland! In about 2021 I didn't think I needed to clear away old leaves from my patch of Louisianas, and that fall I discovered that most of those very narrow rhizomes were all hollowed out by borers. I nearly lost Red Velvet Elvis entirely. Since I started meticulously bagging every scrap of dead leaf by early spring, they are recovering.
