What's eating my iris 'immortality'?

Iris 'Immortality', a reblooming tall bearded iris, is vulnerable to iris borer (in the US), slugs on its autumn rebloom flush, and aphids on the multiple flowering stems it produces. Leaf spot fungal disease often follows borer damage. UK growers face fewer borer risks but should watch for slugs and vine weevil.

Larvae tunnel from leaf edges down into rhizomes; entry wounds show water-soaked streaks and often develop into foul-smelling bacterial rot. Cut back all foliage in autumn to remove overwintering eggs. Squish larvae in leaves in spring; apply nematodes to soil. Inspect rhizomes when dividing and cut out any grubs.

Heavy clustering on the reblooming flower stalks in late summer and autumn; sticky honeydew attracts sooty mold. Strong water jets to dislodge colonies; insecticidal soap or neem oil applied in the evening to avoid harming pollinators.

Holes and silvery slime trails on new leaf fans, and damage to autumn flower stalks. Iron phosphate bait around clumps; coarse grit mulch over rhizomes; night patrols for hand-picking.