Ummmmmm, as a major gardener, you are techically correct... The moles have no use for the plant material...
But here is the rub... Where you have moles, who do the tunneling, you will also have voles... The voles use the moles tunnels, breed in them and the voles do attack the root systems of plants... Their favorite food is hosta roots... One vole can kill a hosta in a matter of a couple days... They also attack yer potaotes and beets in yer veggie garden as well as the roots of many ornimental plants...
We have taken to not only using Permitil but planting out hostas in planters with wire mesh in the bottom to cover the hole which the varments will tunnel thru and kill a hosta in a planter...
I've never known any varment that has any interest in irisesm howeverm so I suspect that what SRS has come up with id most likely the cause of death...
You have to abuse yer irises, Bee, if you want them to thrive... You know... Plant 'um in concrete... lol...