Lace bugs attack many ornamental trees and shrubs in Bucks and Montgomery County including azalea, pieris japonica and rhododendron, often going undetected until the infested plants show severe damage. When searching for signs of this pest look for discolored spots or bleaching of the upper leaf surface. These leaves may become whitish, dry up, and fall off in severe infestations. The adult is 1/8 inch (3mm) long with light brown legs and antennae. Their wings are transparent and lace-like with brown and black markings. Nymphs may be found on the underside of the leaf surface and are colorless as they emerge, but soon turn black and spiny. Deposits of hard, dark, varnish-like spots of excrement may be found on the underside of the leaf surface, especially along leaf veins where the female inserts her eggs. The eggs are white, smooth, and flask-shaped with a neck to one side. Nymphs hatch in early spring and begin feeding on the underside of the leaves before molting 5 times as they become adults. Adults mate and the females lay eggs in the tissue on the underside of the leaves along the veins by mid-summer. Depending on location, there may be 2-3 generations of lace wing per year.
Properly timed soil injections of a labeled insecticide can provide a high level of control.
The bloom time of the host plant should be considered when choosing the specific pesticide and timing of the application. Arborists should only use foliar sprays for immediate activity against the insect. Thorough coverage on the underside of the leaves is essential for good control when applying foliar products. Multiple spray applications may be required as well, making soil applications the product recommendations of choice.
Contact Plant Health Solutions for proper diagnosis and to develop a treatment plan.