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How to identify it
- Adults are tannish brown, about 1/8 inch long, and covered with small cells that make them look like lace. The antennae and legs are pale brown.[1]
- The top of the thorax swells up into a hood that stands about twice as high as the rest of the thorax. The flared, lacy side margins carry a single row of tiny spines.[1]
- Nymphs are small and black or dark brown with very pale legs and antennae. Older nymphs are oval and flat, with spines around the edge of the body.[1][2]
- Look on the lower leaf surface: adults, nymphs, cast skins and dark 'fly speck' excrement collect there under the pale spots.[1][2]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Spider mites and thrips | Their feeding also leaves pale spots on leaves, but lace bug injury is coarser, and lace bugs leave dark excrement specks and cast skins on the leaf underside.[1] |
| Sycamore lace bug | A close relative in the same genus. It feeds mainly on sycamore. Most lace bug species live on a single host or a few closely related ones, and the elm lace bug is found on elms.[2][1] |
| Oak lace bug | Another Corythucha species, found on white, bur and chestnut oaks, where infested leaves turn grayish-white.[2] |
Where it lives
American elm in many Eastern States and southern Canada, and Siberian elm on the Northern Great Plains. NC State describes it as rarely reported.[2][1]
Biology and life cycle
American elm is the only host NC State lists. The USDA Forest Service adds Siberian elm on the Northern Great Plains.[1][2]
Very little has been published on this species' life cycle. NC State considers it highly likely that adults spend the winter in bark cracks and crevices and crawl to the new leaves in spring, as other lace bugs on deciduous trees do.[1][3]
Females probably lay dark brown, elongate eggs like other Corythucha species. Nymphs molt through five stages, and development probably takes at least seven weeks.[1]
Most lace bug species have two generations a year, according to the USDA Forest Service; no source gives a count for the elm lace bug itself.[2]
Damage and signs
Health risk
The sources describe only sap feeding on elm leaves and report no harm to people.[1][2]
Control
Prevention
Turn over a few leaves when spotting appears so you catch the bugs early. Spots already on the leaves will not fade after the lace bugs are controlled.[1][3]
Traps and physical control
On small trees, a hard jet of water from a hose dislodges young nymphs, which often die before they can find their way back to a leaf.[3]
Biological control
Green lacewings, mites and assassin bugs attack lace bugs. Using water sprays or insecticidal soap instead of standard insecticides helps keep these predators around.[3]
Pesticides
Insecticidal soaps and horticultural oils kill only the bugs they hit, so cover the undersides of the leaves.[3]
Elm lace bugs are hard to control on large trees. Most landscape insecticides give adequate control when the tree is small enough to spray well. Imidacloprid applied to the soil beneath the tree early in the growing season should give season-long suppression.[1]
Common questions
- Why are my elm leaves pale and speckled?
- Sap-feeding insects on the leaf undersides are a likely cause. Elm lace bugs leave pale spots on top and dark excrement specks, cast skins and the bugs themselves below. Spider mites and thrips leave finer spotting.[1]
- Do I need to spray for elm lace bugs?
- Not always. On small trees a hard water spray or insecticidal soap on the leaf undersides can help. Large trees are hard to spray, and NC State suggests a soil-applied imidacloprid treatment early in the season instead.[3][1]
Sources
- NC State Extension, “Elm Lace Bug (PDIC Factsheet).” content.ces.ncsu.edu/elm-lace-bug (accessed 2026-11-10)
- USDA Forest Service, “Eastern Forest Insects, Miscellaneous Publication 1175 (W. L. Baker, 1972; scanned copy).” archive.org/details/easternforestins1175bake (accessed 2026-11-10)
- Ohio State University Extension, Ohioline, “HYG-2150: Lace Bugs (D. J. Shetlar, 2011).” ohioline.osu.edu/factsheet/HYG-2150-10 (accessed 2026-11-10)
- iNaturalist, “Corythucha ulmi taxon page (order and family).” www.inaturalist.org/taxa/490070 (accessed 2026-11-10)