Lace bugs are persisting on many trees and shrubs! Consider controlling them to keep the adults from overwintering and repeating the damage next year!
I noticed several hawthorns this week that have been turned yellow by continual lace bug attack this summer. In fact, some trees are beginning to drop leaves. Upon looking closely, there were numerous adult lace bug still on the leaves. The undersurface of each leaf was coated with tar spots (the fecal spots produced by lace bugs), old egg shells and cast skins. Remember that the lace bug species that infest deciduous trees (i.e., hawthorn, basswood, sycamore, willow, oak, serviceberry, walnut and other species) overwinter in leaf litter or under bark flaps as adults.
Controlling lace bugs now will not improve the look of infested trees and shrubs, but knocking out the adult population now should reduce the number of lace bug adults that start infestations next spring. If you plan to use a systemic insecticide at this time, many trees and shrubs are not transpiring well so the systemic insecticide may not be transported well through the plant vascular system. Sprays of systemic insecticides may work better as the insecticides will penetrate the leaf tissues and kill the lace bugs still sucking on the other side of the leaf. Pyrethroids and Sevin are still readily available but sprays must reach leaf undersurfaces. For those wanting minimal impact pesticides, insecticidal soaps and horticultural oils (3%) are also effective against lace buts, but these only kill when sprays contact the bugs.