Azalea Lace Bug does fall damage to azaleas

Lifestyle
November 16, 2021

By Will Summers, Master Gardener


Outside the front door where I work, there are two shrubs that bloom beautifully each spring. At this time of the year, both azaleas look shabby. Their upper leaf surfaces are nearly white and there are small, black spots on the leaf undersides. Nearly every leaf is infected, but some of the new growth seems unaffected. The azaleas look as though they are about to die.

The answer to, “What’s eating my azalea?” is a small insect: Lace bug. This insect is barely one-eighth inch long and about half that in width. The lace bug (Stephanitis pyroides) belongs to a family of insects that includes aphids and mealy bugs. This insect is a very finicky eater and is a major pest on azaleas by sucking the sap from the underside of leaves, leaving the plant unable to feed itself. Eventually, if lace bugs are not controlled, the azalea leaves will drop early and parts of the plant will wither and die.

Lace bugs hatch from eggs in about two weeks. The pale, colorless nymph is a nearly invisible, worm-like creature that begins sucking the plant juices almost immediately. Both nymphs and adults excrete small black dots of honeydew on leaf undersides. This insect gradually darkens and goes through three more stages as a growing, spiny nymph, before reaching the final stage as an adult. In southern Illinois, lace bugs winter-over in the egg stage and emerge early in the spring as leaves appear to begin their life cycle again.
In southern Illinois, there are at least two hatches of lace bugs, one in early spring and a second in early August, from the offspring of the first hatch. All five life stages should be visible on azalea leaf undersides at this time of the year.

Azalea lace bugs were introduced into the United States in the early 1900’s. Lace bugs behaved like most alien species, they accompanied azaleas imported from Asia, and had no natural predators in this country. Only a few native predators are effective at combating lace bugs: Lace wings, lady bugs, assassin bugs, spiders and predaceous mites.

Unfortunately, insecticides kill more of the predators than the target, lace bugs. Insecticidal soaps may help. These are detergent-like soaps that dissolve insects’ natural defenses that protect them from drying-out or completing their life cycle.

There is an outstanding preventive measure to reduce risk of damage from lace bug. Although some azaleas are defenseless against lace bugs, it seems that a few azalea species are resistant from their attacks. If you are troubled by lace bugs in your azalea, there may be no clear natural treatment except the repeated use of strong insecticides. However, there are several azalea varieties that are not affected by lace bugs or seem to have a natural resistance to their feeding. If you are considering adding additional azaleas to your garden or considering replacing azaleas with repeated lace bug infestation, please consider one of more of the following varieties: “Dawn,” “Dram,” “Elsie Lee,” “Ereka,” “Macrantha,” “Marilee,”“Pink Fancy,” “Pink Star,” “Red Wing,” “Salmon Pink,” or “Sunglow.”

Become familiar with the damage done by insects like the Azalea lace wing and spidermites, aphids and mealybugs in general and learn how to recognize damage from this class of insect. For more information concerning flowering shrub pests, or other gardening concerns, please contact your local master gardener or the University of Illinois Extension Service office near you.

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