Lace bugs are present throughout Illinois, feeding on a variety of plant types. Lace bugs are not generally considered a significant ornamental pest, as they don't usually inflict direct harm to plants. However, high populations can reduce the aesthetic appearance of certain plants. Lace bugs feed on a variety of trees and shrubs, including azalea, basswood, cotoneaster, hawthorn, linden, oak, rhododendron, and sycamore. Herbaceous plants that are susceptible to lace bugs include aster, chrysanthemum, and scabiosa. The major plant-feeding lace bug species include Stephanitis spp. and Corythuca spp. Stephanitis spp. are primarily pests of broad-leaved evergreens, whereas Corythuca spp. are pests of deciduous trees and shrubs.
Lace bugs feed on the undersides of leaves; using their piercing–sucking mouthparts, they withdraw plant sap from individual leaf cells, causing leaves to appear stippled and bleached. Damage is similar to that caused by spider mites and leafhoppers; however, lace bugs leave black, tar-spot-like droplets of excrement on leaf undersides. The presence of this black excrement distinguishes lace bugs from spider mites and/or leafhoppers. Very high lace bug populations and extensive feeding may reduce plant vigor, depending on age and size, creating undue stress that increases susceptibility to other insects and/or diseases.
Adult lace bugs are very distinguishable and quite attractive. They have lacy, clear, shiny wings that are held flat over the body. The adults are 1/8 to 1/4 inch long (3 to 8 mm). They tend not to fly but move sideways instead when disturbed.
Female lace bugs lay between 20 to 50 eggs underneath leaves, placing them primarily alongside leaf veins. The eggs are black and shaped like a wine flask. Eggs hatch into shiny black nymphs with spines. Nymphs undergo five instar stages before reaching adulthood. Shed skins on leaf undersides are evidence of nymphs that have transformed into adults. It takes about 30 days to go from egg to adult.
Lace bugs may have as many as three generations per year in portions of Illinois. Stephanitis spp. overwinter as eggs that are cemented onto leaves, whereas Corythuca spp. overwinter as adults in bark crevices and branch crotches. Adult activity begins in the spring when leaves unfold.
Lace bugs tend to occur in higher numbers on plants such as rhododendrons and azaleas that are located in sunny areas, rather than on plants in shady locations.
Control is generally not a concern, as lace bugs are susceptible to an array of natural enemies, including predators such as green lacewings, plant bugs, assassin bugs, minute pirate bugs, spiders, and predatory mites. If feasible, washing lace bugs off plants with a hard stream of water may be effective. In addition, this practice preserves existing natural enemies. If necessary, pest-control materials–including acephate (Orthene), carbaryl (Sevin), cyfluthrin (Tempo), and insecticidal soap–may be useful in managing lace bugs. Because they reside on the undersides of leaves, thorough coverage on leaf undersides is essential.