Scouting for pests: Iris borer
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included
Iris borer larvae initially feed at the tops of plants, chewing holes in leaves and giving leaves a ragged appearance (view images).
They eventually create dark-streaked areas that appear watery. Larvae
migrate down the plant, and then mature larvae bore into leaves a few
inches above the growing medium surface. Mature larvae then feed within
the rhizome, creating large tunnels. The tunneling causes plants to wilt
severely and eventually rot. The adult iris borer is a nocturnal moth
with dark purple front wings and yellow-brown hind wings. Females lay
eggs in plant debris. Iris borer overwinters in the egg stage.
Management: Remove debris from adjacent areas. Clip and remove dead iris leaves and stems to eliminate any overwintering eggs. Contact insecticides need to be applied before the larvae enter leaves. Frequent applications may be necessary in the spring.