What's eating my iris 'jane phillips'?

Iris 'Jane Phillips', a tall bearded iris, faces its worst threat from iris borer in North America and iris leaf spot in both regions. Slugs and snails damage fans in cool wet springs, and thrips can scar petals. Aphids cluster on bud stalks. Rhizome damage from borer grubs often leads to secondary bacterial soft rot.

Caterpillars tunnel into leaves and down into rhizomes, causing ragged-edged water-soaked streaks, then rhizome rot and plant death — mainly a North American problem. In autumn remove and destroy all old foliage where eggs overwinter. In spring squish larvae visible in leaves before they reach the rhizome. Beneficial nematodes applied to soil in early spring help.

Colonies cluster on flower stems and developing buds, causing sticky honeydew, sooty mold, and distorted blooms. Blast off with a firm jet of water; apply insecticidal soap or neem oil; encourage natural predators such as ladybirds.

Ragged holes in young leaf fans in spring; particularly damaging in wet seasons or heavy clay soils. Iron phosphate pellets around the rhizome fans; improve drainage; hand-pick at night.

Silver-streaked or bronzed petal surfaces; flowers may fail to open fully in heavy infestations. Remove badly affected blooms; apply spinosad or insecticidal soap to buds before opening; reduce drought stress.