Lace bugs are small insects, 1/4 to 1/8 inch long, broad, flattened and somewhat rectangular in shape. Their bodies are usually brown or black, but their wings are partially transparent and lace-like. 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. In azaleas, lace bug damage first appears as spotted discoloration or bleaching on the upper surfaces of leaves. In severe cases, leaves can be almost completely bleached and may even drop from the plants.
Common 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).
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. To be effective, sprays must directly contact the lace bugs. Therefore, thorough spray coverage to lower leaf surfaces is necessary with all products.
Lace bug eggs are inserted into plant tissue so they are protected from sprays. Consequently, it may take more than one insecticide application to control the pests, so check your plants again in a week to make sure you have done a thorough job. 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. It is applied around the base of the plant, taken up by the roots and moved through the plant’s vascular system. Because this insecticide must be absorbed by the roots and moved throughout the plant, it may take a couple of weeks to see results.
On the plus side, you may get season-long control of lace bugs from a single application. This insecticide also works well controlling aphids and some scale insects (wax scales and other soft scale). Since this insecticide works within the plant, do not use it around vegetable gardens, fruiting trees or other edible landscape plants. The drench should be applied in the spring according to label directions.
For more information, contact the Christian County Cooperative Extension Service, 270-886-6328.
