Corythucha, commonly known as lace bugs, are small insects frequently found as pests in gardens and landscapes. These distinctive sap-sucking insects belong to the family Tingidae. There are over 2,000 known species of lace bugs, with at least 140 species found in North America. While they primarily feed on the undersides of leaves, their feeding activity can significantly impact the aesthetic appeal and overall health of various plants.
Identifying Lace Bugs
Adult lace bugs are small, ranging from 1/8 to 1/4 inch (3-6 mm) in length. Their distinguishing feature is their flattened, oval-shaped bodies and intricately sculptured, lace-like wings. These transparent or light amber wings are held flat over their bodies when at rest. Their bodies can be various colors, including pale, tan, brown, black, gray, or green, often with mottled patterns.
Lace bugs are most commonly found on the undersides of leaves, where they feed and lay eggs. Many species exhibit specific host preferences.
Recognizing Infestation Signs
The most noticeable sign of a lace bug infestation is the characteristic stippling that appears on the upper surface of affected leaves. This stippling consists of numerous tiny white or yellowish spots, caused by the insects piercing plant cells and sucking out their contents. As infestations worsen, these spots can coalesce, leading to larger bleached-out, yellowish, or bronze areas on the leaves.
Examining the undersides of leaves provides further evidence. You may observe shiny, tar-like spots, which are the insects’ excrement. Additionally, whitish, translucent cast skins of nymphs frequently remain attached to the leaf undersides.
Severe infestations can result in significant leaf discoloration, premature leaf drop, reduced plant vigor, and, in some cases, even the death of smaller trees and shrubs. Plants in full sun are more susceptible to severe damage. Common vulnerable host plants include azaleas, rhododendrons, hawthorns, sycamores, oaks, and various ornamental grasses.
Managing Lace Bug Problems
Managing lace bug problems involves a combination of strategies to reduce populations and protect plants. A simple non-chemical approach is to use a strong stream of water from a garden hose to dislodge nymphs and adults from the undersides of leaves. This method is particularly effective against wingless nymphs, as they struggle to return to the plant. Regular applications, especially early in the season, can help suppress populations.
Horticultural oils and insecticidal soaps offer effective non-chemical control options. These products work by smothering the insects or disrupting their cell membranes, requiring direct contact for efficacy. Thoroughly wetting the undersides of infested leaves is important for these applications. These treatments have low toxicity to people and pets and minimal adverse effects on beneficial insects once dry.
Encouraging natural predators also contributes to long-term lace bug management. Known predators of lace bug eggs, nymphs, and adults include:
Green lacewings
Assassin bugs
Lady beetles
Pirate bugs
Certain mites
Planting a variety of flowering species can attract and support these beneficial insects. Sanitation, such as prompt removal of fallen leaves and plant debris, can help eliminate overwintering adults or eggs, reducing reinfestation potential.
For more severe infestations, chemical control options are available, though they should be used judiciously to avoid harming beneficial insects. Contact insecticides, like pyrethrins, provide quick knockdown when applied directly. Systemic insecticides, such as imidacloprid and dinotefuran, are absorbed by the plant and move through its tissues, offering season-long control with a single application. These systemic products can be toxic to pollinators, so apply them after flowering to minimize exposure to bees. Always read and follow product label instructions carefully, including guidelines for application rates and safety precautions.