Lace Bug on Ornamental Plants

At least 17 species of lace bugs (Heteroptera: Tingidae) are pests of trees and shrubs in the eastern United States. Most lace bug species have a limited host range and may attack only a handful of plant species. Plants that are commonly attacked include azalea, hawthorn, lantana, oak, pyracantha and sycamore.

Biology and Behavior
Lace bugs (Figure 1) are small insects, 1/4 to 1/8 inch long, broad, flattened and somewhat rectangular in shape. Their bodies are usually brown or black, but their wings are partially transparent and lace-like. Immature lace bugs or nymphs (Figure 2) are blackish in color, wingless, and have many small spines projecting from their body.

Figure 1. Azalea lace bug adult

Figure 2. Lace bug nymphs

Females lay eggs on the lower leaf surface along the midrib or lateral veins and cover them with a brownish substance. These dark varnish- or molasses-like spots are obvious when plants are heavily infested. Most species have five nymphal instars before becoming adults. Each generation, from egg to adult, takes about 30 – 45 days. There may be three to five generations each year.

Lace bugs damage plants by inserting their piercing-sucking mouthparts into the underside of leaves and withdrawing chlorophyll and other plant fluids. Females generally cause more damage than males. The upper surface of lightly-infested leaves has a white-dotted, or stippled appearance (Figure 3). Heavy infestations cause leaves to brown and drop prematurely, which reduces growth or kills the plant.

Figure 3. Lace bug damage on azalea

Detecting Infestations
Examine your plants weekly during the spring, summer, and fall. Turn a few leaves over and look for lace bugs with a 10 to 15 power hand lens or shake an infested branch over a white sheet of paper. The insects will fall off and may be more easily identified than on the foliage. The brown spots and stippling may remain on leaves even after pest populations have been reduced.

Cultural Control
Several non-chemical means of reducing lace bug problems exist. One option is to thoroughly spray infested plants with a high-pressure stream of water. However, this approach may only knock the insects off the plants, rather than kill them.

Establish plants according to their growth patterns, keep them healthy, and well-watered. For example, azaleas, which are understory shrubs, tolerate less lace bug damage when planted in full sun and suffering from drought-stress.

Choose varieties or species of plants that are resistant to lace bugs or better tolerate damage.

Biological Control
Very few beneficial insects specialize on lace bugs. However, generalist predators, such as green lacewings, may attack lace bug nymphs and adults. Lace bugs may also be infected by diseases.

Chemical Control
If more than 15% of the foliage is damaged, then an insecticide application is suggested. Insecticidal soaps (e.g., Safer Soap, M-pede) are often a first line of defense against soft-bodied insects. In general, spray plants to run-off or until leaves (top and bottom) are thoroughly wet (check the label for application instructions). Continue to inspect the plants periodically and apply an insecticide if plants become re-infested. Soil treatments are relatively slow in action, but effective for up to 5 or 6 weeks. Systemic insecticides are absorbed more rapidly by plants when they are worked into the soil and watered.

Footnotes
1.
This document is ENY-332 (MG326), one of a series of the Department of Entomology and Nematology, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Date first printed October 1993. Revised: June 2006. Please visit the EDIS Website at http://edis.ifas.ufl.edu.

2.
Eileen A. Buss, assistant professor and Jay Cee Turner, graduate student, Department of Entomology and Nematology, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.