Corythucha ciliata, or the Sycamore Lace Bug, is a small insect pest primarily affecting sycamore trees. Native to eastern North America, it has become an invasive species in Europe, Australia, and China, spreading via human transport. While generally not fatal to mature trees, infestations can reduce a tree’s vigor and aesthetic appeal.
Identifying the Sycamore Lace Bug and Its Life Cycle
The adult Sycamore Lace Bug is small, about 3 to 4 mm long, with a flattened body. Its most distinguishing feature is its whitish, “lacy” wings and pronotum, which cover its body and head. A small brown spot is often present on each wing cover. Nymphs, the immature stage, are oval, dark, and spiny, resembling miniature adults but lacking wings.
Sycamore trees (Platanus species), particularly American sycamore (Platanus occidentalis), are the primary host plants for this insect. While sycamores are the preferred host, the lace bug has also been observed to feed on other trees like ash, hickory, and mulberry, though less commonly. All life stages of the sycamore lace bug reside on the underside of leaves.
The Sycamore Lace Bug often has several generations per year, particularly in warmer climates. Adults overwinter in protected locations like under loose sycamore bark or in nearby cracks, able to withstand temperatures as low as -10°F. In spring, as new leaves emerge, adults become active, feeding and laying barrel-shaped eggs on the undersides of leaves, often along leaf veins. A single female can lay 200-350 eggs.
Eggs hatch into nymphs, which undergo five developmental stages (instars) before reaching adulthood. Complete development from egg to adult takes approximately 30 to 45 days, depending on temperature.
Signs of Infestation on Trees
Sycamore Lace Bug feeding creates distinct visual signs on affected trees. They use piercing-sucking mouthparts to extract sap from leaf cells, mainly on the undersides of leaves. This causes characteristic white or yellowish stippling, appearing as tiny spots on the upper leaf surface. As infestations intensify, these spots can merge, leading to larger areas of discoloration that may appear yellow, bronze, or bleached.
The underside of infested leaves reveals additional evidence. Dark, tar-like fecal spots (frass) deposited by feeding nymphs and adults are visible. Translucent, shed nymphal skins also cling to the leaf surface. In severe and prolonged infestations, sycamore leaves may turn brown prematurely and drop, especially in late summer. While chronic feeding can stress the tree and reduce its vigor and aesthetic value, it generally does not lead to tree death unless combined with other significant stressors over several consecutive years.
Effective Management and Control
Maintaining sycamore tree health helps them tolerate Sycamore Lace Bug infestations. Proper watering and fertilization, especially during dry periods, supports tree vigor and reduces pest damage. Planting sycamores in appropriate sites where they can thrive also contributes to their resilience against pest pressures.
For smaller trees or early infestations, hosing down leaves with a strong stream of water is a simple physical control. This dislodges nymphs and adults, reducing their population. Repeating this process regularly can be effective. Natural predators like lacewings, assassin bugs, minute pirate bugs, and spiders also prey on lace bugs. Encouraging these natural enemies by avoiding broad-spectrum insecticides contributes to biological control.
For severe infestations, chemical control options may be considered, often emphasizing integrated pest management. Horticultural oils and insecticidal soaps are effective, especially when applied early to target nymphs and eggs. These products smother insects and have a lower impact on beneficial insects than other chemical treatments. For widespread or persistent infestations, systemic insecticides, such as imidacloprid, can be used. These products are absorbed by the tree’s vascular system, making its sap toxic to feeding lace bugs. Systemic treatments are often applied by professionals, either as soil drenches or trunk injections. Timing is important; treatments are most effective when nymphs are active, typically in late spring or early summer. Choosing resistant tree varieties can be a preventative measure for new plantings, though specific resistant sycamore varieties are not commonly highlighted.