Yellowing Hackberry Trees Usually Means Lace Bugs

Again this year we are experiencing a bumper crop of hackberry lace bugs. Lace bugs are present every year on several of our common deciduous trees, but only occasionally are the populations large enough to be noticed. Other trees besides hackberry have lace bugs, but hackberry seems to suffer the most sever and noticeable symptoms. Though lace bugs from different trees all look alike, each tree species is infested with a different species that is named after the host plant; for example, hackberry lace bug Corythucha celtidis is on hackberry, sycamore lace bug C. ciliata is on sycamore and so forth.

Lace bugs are sap feeding insects. They rest on the underside of the leaves and pierce the leaf epidermis with their sucking mouthparts. This causes the characteristic bleached appearance of the leaves that actually is clusters of tiny whitish dots or chlorotic specks on the upper leaf surfaces. Plants heavily damaged by lace bugs usually have the underside heavily speckled with small, black, shiny "varnish spots" (excrement).

Lace bug adults have the wings and thorax beautifully sculptured with an intricate pattern of veins that resembles lace. The wings and thorax are flat on top and appear white. The wings extend out over the sides of the black body. Adults are approximately 3/8-inch long. The nymphs are black, spiny and pointed at both ends. It is typical to find clusters of empty nymphal "shells" (exoskeletons) on the leaf undersides.

Little if any significant benefit will be achieved trying to control lace bugs this late in the season. Most damage is done by the nymphs earlier in the season and spraying will not return green color to the already-damaged leaves. Expect damage to continue to attract attention as symptoms accumulate. Some of the more heavily damaged trees will defoliate early.

Though treatment is not justified from the tree's perspective, there may be adequate nuisance created by lace bugs dropping from infested trees to warrant control attempts. Though the lace bugs are harmless to people, pets, structures, and landscape plants there may be a desire to treat to alleviate the annoyance. Insecticides for lace bugs include insecticidal soap, Sevin, Orthene, malathion and Isotox.

This article originally appeared in the August 11, 1995 issue, p. 124.


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