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Iris Borer

Iris borer is the most detrimental insect pest of iris plants. The name derives from the insects tunneling throughout the plants. Eggs are laid on leaves in the fall and stay on the plant through the winter. When spring arrives, eggs hatch and larvae move to fresh spring foliage and begin tunneling. They make their way down the stem to the rhizome (an underground stem) of the iris plant. Larvae create a hole in the rhizome so they can enter the surrounding soil to pupate. After two to three weeks, adult moths surface from the soil. Symptoms of this pest include dark lines on leaves, rough leaf margins, or even soft rot in the rhizome, which is evident by a foul odor.