Lace bugs use their sucking mouthparts to feed on plant sap. Damage ranges from a few scattered tiny white-to-yellow spots to bleached-white leaves that drop prematurely. Common lace bug species in Kentucky feed on azalea (azalea lace bug); hawthorn, cotoneaster, pyracantha, Japanese quince (hawthorn lace bug); rhododendron and mountain laurel (rhododendron lace bug); and ash, hickory, mulberry, and sycamore (sycamore lace bug).
Lace bugs can be confirmed as culprits by looking at the undersides of spotted leaves for the insects, white cast skins, tarry waste spots, or eggs (larger dark spots along leaf midribs)(Figure 1). Adults are about 1/8 inch long with lace-like wings that cover the abdomen (Figure 2). Nymphs are dark and spiny.
Tolerate light to moderate feeding; healthy plants should not harmed by this level of damage. When practical, prune damaged foliage and follow sound practices to promote plant health.
Insecticidal soap and horticultural oils will control lace bugs with minimal impact on natural enemies; however, thorough spray coverage to lower leaf surfaces is necessary with all products.
Lace wing eggs are inserted into plant tissue so they are protected from sprays. Consequently, more than one application may be needed for control. These applications must be made at the first signs of leaf spots to be effective.
A soil drench with an imidacloprid product can provide good preventive control where chronic infestations are a problem. The drench should be applied in spring according to label directions.
By Lee Townsend, Extension Entomologist