We are seeing considerable lacebug feeding damage in Delaware landscapes at this time. The following is more information on the subject.
Lace bugs use their sucking mouthparts to feed on plant sap. Damage ranges from a few scattered tiny white to yellow spots on the upper surfaces of leaves to bleached white leaves that drop prematurely in late summer. Lacebugs commonly 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). The adult is about 1/8 inch long with lace-like wings that cover the abdomen. Nymphs are dark and spiny.
Tolerate light to moderate damage as much as possible; often the plant is not harmed by these insects. Prune damaged foliage if practical and follow sound practices to promote plant health. Insecticidal soap and horticultural oils can be used for control with minimal impact on natural enemies; most other insecticides will provide control, as well. 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 the spring according to label directions.
Azalea lacebug adult. Photo from the Pest and Diseases Image Library, Bugwood.org
Azalea lacebug damage. Photo by Whitney Cranshaw, Colorado State University, Bugwood.org
Information from Lee Townsend in the current edition of the Kentucky Pest News http://www.uky.edu/Ag/kpn/kpn_09/pn_090804.html