Iris borers belong to the family of Lepidoptera. Adults are large moths with a wing spread of 3.8-5.0 cm. The wings are covered with scales, brown and smoky dark gray on the front wings, and yellowish on the hind wings. Forewings have a scalloped outer margin and a black streak along the reniform spot. Full-grown caterpillars are cylindrical, smooth, and up to 4.5 cm long. Caterpillars are the most destructive insect pests of the iris.
Iris borers overwinter as eggs on brown dried leaves of both iris and other types of plant debris. Eggs hatch in late spring and larvae mine into the leaves and continue down toward the rhizome. The last instar larvae leave the rhizome to pupate in the soil. The moths emerge in late summer or fall and lay up to 100 eggs. There is only one generation of iris borer each year.
Iris borer is the most serious pest of the iris. The caterpillars chew holes into the leaves creating a water-soaked spot. The larvae tunnel down toward the rhizome and may completely hollow out one or more rhizomes. Affected rhizomes also are rotted by soft rot bacteria that colonize the caterpillar feeding areas and cause the rhizomes to become slimy, soft, and have a foul smell. The attacked plant will discolor, wilt, and die.
Iris borer is the most serious pest of the iris. The caterpillars chew holes into the leaves creating a water-soaked spot. The larvae tunnel down toward the rhizome and may completely hollow out one or more rhizomes. Affected rhizomes also are rotted by soft rot bacteria that colonize the caterpillar feeding areas and cause the rhizomes to become slimy, soft, and have a foul smell. The attacked plant will discolor, wilt, and die.
