The sycamore lace bug is a common pest of sycamore but has also been reported on other host plants. The adult life stage overwinters in sheltered areas, often the exfoliated bark of the sycamore itself. Adults are tiny, whitish in color, with lace-covered wings and approximately 0.12 inches in length. With warming spring temperatures and the development of host plant leaves, the adult lace bugs again become active. Adult females will lay their eggs and attach them to the undersides of host plant leaves with a sticky brown substance. Often these eggs are hidden in the hairy parts of the leaf undersides. Each female may lay up to or at least 284 eggs (Wade, 1917). Egg hatch occurs in a few days, and the sycamore lace bug nymphs (immatures) begin feeding with piercing-sucking mouthparts on the undersides of the host plant leaves. This type of feeding leads to the characteristic chlorotic (yellow, stippling) flecks that are visible from the upper surface of the host plant leaf. Nymphs are dark black in color and have spiny projections on their bodies. Nymphs are wingless until they mature fully into the adult life stage. Fourth instar nymphs are more likely than the earlier instars to distribute to new leaves to feed. Most feeding initially occurs on the leaf to which the egg was attached. The length of time it takes the sycamore lace bug to develop from egg to adulthood is approximately 30 days (Johnson and Lyon, 1991). Two or more generations may occur per year. For example, in the warmer locations of this insect's range, up to five generations can occur per year. By late summer, it is possible to find adults and nymphs feeding together on the undersides of host plant leaves. As the adults and nymphs feed, they excrete shiny, black, almost varnish-like spots of excrement on the undersides of their host plant leaves. The sycamore lace bug is a native North American insect that is an example of an invasive species that was accidentally introduced into Europe from North America. It was first discovered in Italy in 1964. In Europe, the sycamore lace bug is also associated with species of fungi which it may vector to its European host plants. These fungi are Ceratocystis fimbriata and Apiognomonia (previously Gnomonia) veneta (Maceljski, 1986).
Feeding by the immatures and adults of the sycamore lace bug occurs on the underside of host plant leaves, however the feeding damage is eventually visible on the upper leaf surface. The removal of host plant fluids from the underside of the leaf using piercing-sucking mouthparts leads to chlorotic (white or yellow) stippling or flecks on the upper leaf surface. Eventually, this feeding damage may be so extensive that the foliage may become bronzed. Additionally, if the population is large enough, this feeding damage may lead to premature leaf drop. This defoliation may occur late in the summer. It is possible that several consecutive years of severe lace bug damage and premature leaf drop, as well as other combined stressors, may lead to the mortality of trees. This may be more likely to happen to trees planted on poor sites. For example, heavy infestations are more common in urban areas than rural or natural locations. Damage from sycamore lace bug feeding may be exacerbated by drought or dry conditions.
As soon as new sycamore leaves expand, the overwintered adult sycamore lace bugs can travel to the undersides of the leaf to feed and begin egg laying. Visually monitor for the presence of these insects as soon as temperatures allow in the spring. Chlorosis, bronzing, or premature leaf drop (if it occurs) will not happen until later in the summer. Look for the life stages of this insect, as well as their tar-like spots of excrement, on host plant leaf undersides.
The size of the primary hosts of the sycamore lace bug as well as the location of the insect feeding (leaves in the canopy) make cultural management options targeting this insect difficult. However, the single most important cultural management option for sycamore lace bug would be planting these host plants properly and on the correct site. Prevention of other stressors (abiotic and biotic) will help prevent premature leaf loss from sycamore lace bug feeding. For example, trees located in natural or sufficient sites often only suffer aesthetic damage from this insect that is not damaging to the overall health of the plant and requires no management.
Lacewings, assassin bugs, minute pirate bugs, spiders, and predaceous mites are all listed as natural enemies of the sycamore lace bug (Wade, 1917; Johnson and Lyon, 1991). In North Carolina up to 1/4 of the eggs of the sycamore lace bug may be inviable, suggesting an additional mortality factor. As such, reduced risk chemical management options should be utilized in urban settings if chemical management options are being considered. Reduced risk options will help protect natural enemy populations. The CABI Compendium (online) lists additional species of predators or pathogens that may utilize sycamore lace bugs.
Abamectin (NL)
Acephate (NL)
Azadirachtin (NL)
Beauveria bassiana (NL)
Bifenthrin (NL)
Carbaryl (L)
Chlorantraniliprole (NL)
Clothianidin (NL)
Cyfluthrin (NL)
Deltamethrin (L)
Dinotefuran (NL)
Fenpropathrin (NL)
Flonicamid+cyclaniliprole (N)
Gamma-cyhalothrin (L)
Horticultural oil (L)
Imidacloprid (L)
Insecticidal soap (NL)
Lambda-cyhalothrin (L)
Malathion (L)
Permethrin (L)
Pyrethrin+sulfur (NL)
Spinetoram+sulfoxaflor (N)
Active ingredients that may be applied systemically include: Abamectin (injected), acephate (injection), azadirachtin (injection, soil drench), chlorantraniliprole (soil drench), clothianidin (soil drench), cyantraniliprole (NL), dinotefuran (soil drench), and imidacloprid (soil drench).
Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.
Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.
