Macroonocutua onusta (Iris Borer) is a huge brown and smoky dark grey moth with an 18–21 mm FW length.
Caterpillars develop cylindrical, smooth, and up to 1 3/4″ long when fully grown. Pupae are glossy and dark brown to practically black.
The wing span of adult moths is 1 1/2-2 inches. Scales cover the wings, purplish-brown on the front and yellowish on the back. The surface of the eggs is not smooth but rather sculpted.
They change color from a creamy tint with a greenish tinge to lavender. They’re mainly found in nooks and rough areas on dried, brown, dead leaves.
Host plants:
The bearded iris is the most afflicted, yet it can generally withstand the onslaught. Irises from Siberia and Louisiana are less typically attacked, yet they are usually killed.
Territory:
Iris borer may be found across the eastern United States, wherever iris plants are planted as hosts.
Damage caused by Iris Borer:
The iris borer affects all iris species, including the native blue flag and gladiolus and blackberry lilies on occasion. While iris borer larvae graze on the leaves, the bigger larvae feed on the rhizomes that cause the most harm. Before pupating, older larvae may hollow out more than one rhizome. Plants that the rhizome assault has injured are weaker and vulnerable to bacterial soft rot. Since their rhizomes are planted deeper, Siberian irises may be less vulnerable to iris borer infestation.
Life history and Habits:
Macronoctua onusta, or iris borers, are the most devastating pests of the iris. Iris bore eggs overwinter on the stalks of iris plants or in the trash around their bases. The caterpillars ascend the plant after hatching in the spring and continue burrowing down through the new leaves towards the rhizome. The larvae will be plump, pink, and have a light stripe along the back with a brown head. The iris borer will reach the rhizome in late June or early July, depending on your zone. While in the rhizome and the soil, the borer is most vulnerable to Ecomask. The adult moth will emerge shortly after, mate, and lay its eggs on or near the old plants.
