Species

Common Name: Rhododendron Lace Bug
Stephanitus rhododendri
Class: Insecta
Order: Hemiptera

There are multiple types of lace bugs, including the sycamore lace bug, hawthorn lace bug, hackberry lace bug, oak lace bug, basswood lace bug, azalea lace bug, andromeda lace bug, western sycamore lace bug, and avocado lace bug.

Host/Site

Rhododendron lace bugs are pests of species of rhododendron, sycamore, azalea, and evergreen trees. The Rhododendron lace bug can infest over 120 types of rhododendrons, as well as mountain laurel and leucothoe.

Lace bugs, in both the nymph and adult stages, live on the underside of leaves. Preferring new leaves, they feed on the sap, leaving visible yellow/white stipples on the upper side of the host leaf.

Identification

Appearance
Adult lace bugs have sculptured wings covered with veins that look like lace. They are transparent in coloration , and also can be white or yellow.

Adult lace bugs approximate 1/8 inch in length, by 1/16 inch in width. They are generally rectangular in shape. Nymphs are oval and have visible spines.

Indicators
To assess whether the damage is from a lace bug, look for the pale yellow, translucent wing coloration. Also, look for nymphs, as well as characteristic leaf damage. Damage includes yellow stipples on the upper side of the leaf as well as excrement concentrations along the veins underneath.

Life Cycle
Rhododendron lace bugs overwinter in eggs. The eggs are situated near the vein of the leaf and coated with the female's excrement.

Nymphs hatch usually in mid-May. They feed on the underside of the leaf and molt in stages until becoming adults.

Once adults, lace bugs mate and lay eggs in mid-summer. There can be multiple generations in a given year.

Natural Enemies

Natural enemies to lace bugs include: Green Lacewings (adults and larvae), predatory mites, assassin bugs, Lady Beetles, jumping spiders, and Minute Pirate Bugs.

Monitoring

Lace bugs are generally noticed only after an infestation begins. If you have a susceptible plant, check for signs before spring arrives. Eggs can be located by brown excrement on the underside of leaf veins. This indicates that the female has laid eggs and coated the region for security.

Once a hatch has occurred, nymphs and adults can be located on the underside of a leaf. If damage has already occurred, yellow stippled marks will be visible on the top of the leaf.

Action Threshold

Evergreens tend to keep the damaged leaves from one season to the next. Though lace bugs should be controlled, their removal will not lessen the visible damage on the leaves—it will simply impede the possibility of greater damage.

Eliminating lace bugs before hatching is necessary to avoid visible damage to leaves.

Once an infestation is noticed, however, it is recommended that lace bugs be controlled for the health and visual appearance of the plant/tree.

One positive aspect of lace bugs is that they often remain on one plant without spreading to surrounding susceptible plants.

Cultural and Physical Controls

These physical control methods can greatly reduce the chance for lace bug infestation.

When planting, be sure to plant lace bug susceptible plants in areas that will receive protection from the sun. Lace bugs prefer sunny areas, and lace bugs seem to avoid shaded plants. Many of the plants Rhododendron Lace Bugs inhabit prefer shade environments so be sure to plant them in these areas.

Use a hose or a hard jet of water to remove nymphs as they begin hatching in spring. Nymphs will die once dislodged from the leaf.

Biological Controls

Preserve and encourage growth of natural enemies (listed above) by mulching soil with organic material, shading plants from excessive sun exposure, and maintaining a diverse variety of species in the garden. Beneficial insects are attracted to plants in the mint, daisy, and carrot families.

Chemical Controls

IPM approved chemicals such as natural insecticidal soaps and horticultural oils are recommended for lace bug control. Soaps must be applied directly to the undersides of the leaves on which the nymphs are hatching and feeding. Additional applications of soaps may be necessary, and they must physically contact the nymphs for successful results.

Insecticides will not restore previously damaged leaves, but only prevent further damage. Insecticidal soaps and narrow-range oils are IPM appropriate in that they have a low toxicity to humans and a less detrimental impact on beneficial insects and the environment than generic insecticides.

References

Day, Eric. "Lace Bugs." Etymology Publication. Aug. 1996. Virginia Cooperative Extension. 22 Jan 2009. <http://www.ext.vt.edu/departments/entomology/factsheets/lacebug.html>.

Dreistadt, S.H., and E.J. Parry. "Lace Bugs." Pests in Gardens and Landscapes. Aug 2006. UC IPM Online. 22 Jan 2009. <http://www.ipm.ucdavis.edu/ PMG/PESTNOTES/pn7428.html>.

Gorsuch, Clyde S., and J McLeod Scott. "Azalea and Rhododendron Insect Pests." Home and Garden Information Center. May. 2004. Clemson University Extension. 22 Jan. 2009. <http://hgic.clemson.edu/factsheets/hgic2051.htm>

"Lace Bugs." URI Green Share. 1999. University of Rhode Island Extension. 22 Jan 2009.
<http://www.uri.edu/ce/factsheets/sheets/lacebugs.html>

"Rhododendron Lace Bug." Center for Integrated Pest Management. North Carolina State University. 22 Jan 2009. <http://ipm.ncsu.edu/ag189/html/Rhododendron_Lace_Bug.HTML>.

Shetlar, David J. "Lace Bugs." Etymology. Ohio State University Extension. 22 Jan 2009.
<http://ohioline.osu.edu/hyg-fact/2000/2150.html>