Iris – Leaf Spot

Q: I have many brown spots on the leaves of my iris. Can you tell me how to rectify the situation?

A: Iris leaf spot is a common malady of iris. The brown spots are inconspicuous until flowers appear. Afterwards they may coalesce and cause the top half of the leaf to die. Though the disease does not attack flowers or roots, it can weaken the plant due to leaf loss. Since the fungus overwinters on old foliage, cut diseased leaves at ground level in October. Dispose of them in the garbage. If you are a real iris fancier you can spray with a fungicide containing chlorothalonil or mancozeb when the leaves are four to six inches high. Repeat every ten days. Be sure to add one-fourth teaspoon of liquid detergent to each gallon of spray to aid in wetting the waxy foliage.

iris leaf spot