Elm Lace Bug – Corythuca ulmi

Elm Lace Bug: Appearance, Territory, Damage and Life

Latin name: Corythucha Ulmi

Appearances: Adults have a hood that is twice as tall as the rest of the thorax and looks to be inflated. The exterior edges are lacey and extended (the paranota). A single row of minuscule spines along the paranota’s margin. These 1/8-inch long, tannish brown beetles have a lace-like appearance thanks to their coating of tiny cells. The legs and antennae are a light brown color. The lace bug is a cream-colored, 3 x 1.5 mm (1/10 inch) long insect. The outer margins of the netted, lacy wings—which are decorated with black or brown patches—exceed the body’s contour and are kept flat over the body. The small size and transparent wings make it harder to see without careful observation.

Host plant: For the elm lace bug, only the American elm is recognized as a host plant. Symptoms of infestation include pale spots on the top of the leaves, excrement-stained spots, cast skins, and sometimes elm lace bugs and their nymphs on the lower leaf surface.

Territory: In all areas of Oklahoma where their host plants are available, different species of Corythucha can be found.

Damage insect caused: The upper leaf surface develops yellow or pale patches as a result of elm lace bugs feeding on the lower leaf surface. While lace bug damage is rougher, it resembles thrips and spider mite damage in several ways. The leaves may almost become white if there is excessive feeding. On the underside of the leaf, lace bugs also leave “fly specks” or feces.

Life cycle and habits: In cracks in the bark, crotches in branches, or other similar protective locations of their host plants, lace bugs overwinter as adults. They appear around the time that the host’s springtime leaves begin to grow. A sticky brown material holds the tiny black eggs to the underside of the leaves. The eggs hatch after a few days, and the nymphs start eating the leaves. They puncture the leaf with their sucking mouthparts and remove the fluids and cell contents. From egg to adult, the life cycle can be completed in around 30 days. In Oklahoma, several generations take place annually.