Watch for signs of iris borers before it’s too late


By Jeff Rugg | Creators Syndicate

Q: My iris plant leaves are dying one at a time. I have a lot of irises, and the dying plants are scattered through the whole yard. They get the same watering and care as iris plants that are still green and not showing any problems. I want to stop this problem quick. Any ideas on what it could be?

A: Iris borers are the caterpillars of the night-flying iris borer moth. The tiny caterpillars eat ragged holes along leaf edges and then work their way into the center of the leaf.

The weakened leaves will hang over as though it were wilting from lack of water when they really have an insect problem.

iris borers

The caterpillars then burrow down into the iris rhizome. The roots of the iris can then get bacterial diseases that kill the plant. As the root system dies, the leaves look wilted again, but this time it is a combination of fewer roots and diseases.

The few stems that are left are in for a lot of trouble because the adult moths will find fewer stems to attack than before.

What to do

To clean out the borers, watch for the tops of the leaves turning brown and starting to wilt. If a leaf shows these signs, follow it down and see if there are any soft, mushy areas down near the base. If you can pull the leaf off with a light tug, look inside by holding it up to the light or opening it up.

If a caterpillar is inside, just step on it. If it is not, check down at the leaf base to see if it has entered the rhizome. Pry it out with a stick, and step on it.

You may want to apply a borer-killer insecticide if you cannot find the larvae. At this time of year, you can dig up each of the affected iris plants, clean out the borers and then replant them.

Email questions to Jeff Rugg at


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