Lace bugs are common, sap-sucking insects that target many ornamental trees and shrubs, including Azaleas, Rhododendrons, and Sycamores. These tiny pests pierce leaf tissue and extract chlorophyll, causing significant cosmetic damage that can reduce plant health over time. This guide offers actionable steps for removing existing infestations and implementing cultural practices to prevent their return to your landscape.
Identifying Lace Bugs and Their Damage
Lace bugs are named for the distinctive, intricate, lacy appearance of their wings, which are held flat over their small, rectangular bodies. Adult insects are typically about one-eighth of an inch long, making them difficult to spot on the upper side of foliage. The immature stages, known as nymphs, are wingless, spiny, and dark-colored. Both adults and nymphs primarily feed on the concealed undersides of leaves.
The most recognizable sign of an infestation is stippling damage on the upper surface of the leaves. This feeding damage first manifests as tiny, pale yellow or white spots where chlorophyll has been removed. As feeding continues, these spots merge, giving the entire leaf a bleached, silvery, or bronzed appearance. A definitive sign is the presence of small, dark, sticky droppings, called “frass” or “tar spots,” visible on the underside of the affected leaves.
Immediate Non-Chemical Control Methods
Immediate control methods focus on physically eliminating the soft-bodied nymphs when they hatch in early spring. Insecticidal soaps and horticultural oils work by directly coating the insect’s exterior, leading to suffocation or cellular disruption. For these contact treatments to be successful, thorough coverage of the leaf underside is necessary, as the product has no residual effect after it dries. Use a commercial insecticidal soap solution at a 1% to 2% rate.
Application should be timed to coincide with the first generation of newly hatched nymphs, typically in early to mid-spring, and must be performed in the early morning or late evening to prevent leaf burn. A strong jet of water from a garden hose can physically dislodge the wingless nymphs from the undersides of the leaves. For heavily infested branches, pruning is a viable method to remove large concentrations of eggs and insects, which should then be bagged and discarded.
Encouraging natural predators offers a long-term, non-chemical solution that maintains a balanced garden ecosystem. Effective predators include green lacewing larvae, lady beetles, and assassin bugs, which feed on lace bug eggs and nymphs. You can attract and retain these beneficial insects by planting nectar-rich flowers such as dill, fennel, and yarrow nearby. Avoiding the use of broad-spectrum pesticides is also important, as these chemicals kill beneficial insects just as readily as they kill pests.
When to Use Targeted Chemical Treatments
When non-chemical methods fail to manage a severe, recurring infestation, targeted chemical treatments become an option. These products are divided into contact sprays and systemic insecticides. Contact insecticides, such as pyrethroids, kill lace bugs on contact and require meticulous application to the leaf undersides. Systemic insecticides are absorbed by the plant’s roots or bark and move throughout the vascular system, making the plant sap toxic to sap-sucking pests.
Common systemic insecticides, such as neonicotinoids like imidacloprid and dinotefuran, provide season-long control with a single application. However, these products are highly toxic to pollinators because the active ingredient is distributed into the plant’s pollen and nectar. For flowering plants, such as Azaleas and Rhododendrons, systemic application must be avoided during the blooming period to protect bees. A newer class of systemic insecticides, butenolides like flupyradifurone, is considered safer for bees, though they may still pose a risk to beneficial insects like lacewing larvae.
Long-Term Prevention and Host Plant Management
Long-term prevention relies on minimizing plant stress and selecting plants less susceptible to infestation. Lace bugs preferentially target plants growing in full sun or those weakened by drought conditions. Azaleas and Rhododendrons should be sited in partial shade to reduce their vulnerability.
Proper cultural practices help plants remain vigorous and naturally resistant to pests. This includes deep, infrequent watering during dry periods to encourage a robust root system, avoiding shallow watering that stresses plants. Applying mulch around the base of the plant helps maintain consistent soil moisture and temperature, further reducing drought stress.
Selecting resistant varieties is the most effective preventative measure for new plantings. For Azaleas, highly resistant cultivars include the Encore series varieties such as ‘Autumn Amethyst,’ ‘Autumn Twist,’ and ‘Autumn Royalty,’ which show reduced feeding preference.