Iris Rust Identification and Control

Q: My iris leaves have distinct yellow streaks. The blooms coming up are healthy.

A: This is iris rust. Rust is a common problem on iris. Dew, rain, fog, high humidity and overhead watering all encourage the development of iris rust. The best way to control rust is to prevent it. Remove and destroy old foliage in the fall. Don’t plant new healthy irises in a spot where you previously have had rust problems.

If rust occurs, remove infected foliage.

Fungicides containing chlorothalonil (click for sources), myclobutanil (click for sources), and mancozeb (click for sources) will help control rust.