What's eating my iris?

Iris borers are the most destructive pest of bearded iris, tunneling into rhizomes and inviting bacterial soft rot. Aphids colonize buds and foliage, and slugs rasp young leaves and flowers. Thrips can streak petals. Good garden hygiene — removing dead foliage in fall — breaks the borer's life cycle and is the key defense.

Caterpillars tunnel down leaf margins into rhizomes; infected rhizomes turn mushy with bacterial soft rot and smell foul. Remove and burn all dead foliage in autumn to destroy overwintering eggs. Dig and cut out infested rhizomes; dust with a systemic insecticide in early spring when leaves are 4–6 in tall.

Dense colonies on buds and soft new leaves cause distorted growth, sticky honeydew, and sooty mold. Knock off with a strong water spray; apply insecticidal soap or neem oil. Natural predators (lacewings, ladybugs) provide good control.

Irregular holes and silvery slime trails on young leaves and petals, worst in wet spring weather. Apply iron phosphate slug bait around plants; remove daytime hiding spots (debris, dense mulch). Beer traps are effective for small gardens.

Silver-white streaking or flecking on petals and foliage; petals may brown at edges prematurely. Remove and destroy heavily infested blooms. Spinosad or insecticidal soap sprays applied at petal-opening stage reduce thrips numbers.