Chyrsanthemum lace bugs (Corythuca mamorata) have settled in on some of our late-season flowering perennials, especially New England asters (Symphyotrichum novae-angliae) and goldenrod (Solidago sp.). Extensive lace bug feeding on the lower part of plants causes discoloration and leaf die-back. This specific lace bug may also be found on other plants in the Asteraceae including chrysanthemum, sunflower, black-eyed Susan, and ragweed.
Chrysanthemum lace bugs feed on both the upper and the underside of leaves leaving behind pale colored speckling and tar-like droplets of excrement on leaf surfaces.
Lace bugs a have piercing-sucking mouthpart that removes plant sap from leaf tissue. Ouch!
Lace bug damage may be mistaken for that of the two-spotted spider mite, though there are a couple of notable differences. Spider mite populations also produce a fine webbing on leaves, stems, and flowers. Spider mites do not leave behind tar-like specks of excrement as lace bugs do.
Female lace bugs insert eggs along leaf veins. These eggs have a yellow cap. Here they have been inserted along the leaf midrib. Once hatched, nymphs are tiny, shiny, and spiny. They go through five stages of development before reaching adulthood.
Lace bug management is usually not necessary as natural enemies can keep populations in check. Common natural enemies include ladybugs, lacewings, minute pirate bugs, spiders, plant bugs, and assassin bugs. However, large populations can cause herbaceous garden plants to become unsightly.
Lace bug management strategies are similar to those used for two-spotted spider mites. The first approach is to spray nymphs and adults with heavy streams of water. To remove Chrysanthemum lace bugs, direct the spray to the upper AND underside of leaves. Additionally, insecticidal soaps and horticultural oils that control insects through direct contact can also be applied. These are generally safer on natural enemies and beneficial insects. Be aware that these methods will not impact eggs, only nymphs and adults, and will likely need to be repeated for effective control.
Systemic insecticides can be used when the above methods fail to provide the desired control. As was previously reported by Joe Boggs here, "systemic insecticides are effective in controlling plant-sucking insects and also present a lower risk to non-target insects as long as they are applied as soil drenches/injections or bark sprays (e.g. dinotefuran) rather than foliar sprays. Systemic insecticides effective against lace bugs include flupyradifurone (e.g. Altus), and acephate (e.g. Orthene, Lepitect), as well as neonicotinoids such as dinotefuran (e.g. Safari, Transtect) and imidacloprid (e.g. Merit, Xytect)."