When azaleas are in a garden, azalea lace bugs are sure to follow. The good news is these insects, that discolor the leaves of azaleas, can be controlled.
Lace bugs live on the underside of leaves and damage their hosts by piercing leaves with their straw-like mouthparts and removing the plant’s juices. Infested leaves have tiny yellow spots on the top surface and are discolored with dark, varnish-like excrement and old insect parts on the underside. Azalea plants begin to look unhealthy as insect numbers increase through spring and summer.
Azalea lace bugs spend winter as eggs on the underside of azalea leaves. They hatch in early to mid-March and then begin to feed and develop into adults.
Lace bugs complete their first generation by late April. They increase in number throughout the remainder of spring, summer and fall. These insects can complete three to five generations in a single growing season. In late September adult lace bugs, in their final generation of the season, lay eggs that will carry the population through winter.
The key to easily controlling azalea lace bugs is to properly time control efforts.
Inspect plants in early spring to see if insects are present. Look for leaves that are whitish to yellow on the top surface (they may be mottled in appearance) and have small, dark, varnish-like spots on the undersides. If leave damage is heavy continue to check plants every week for small lace bugs, which should begin to be visible in late March through April.
Early to mid spring is the best time to control the first generation of the bugs. Proper insecticide application timing will reduce need for further sprays during the rest of the growing season.
Insecticidal soap, horticultural oil, neem oil and most synthetic insecticides provide good control of lace bugs on azaleas. When using these types of chemicals, make sure to spray the backs of the leaves.
Systemic insecticides available for use against lace bugs include dinotefuran (Safari), imidacloprid (Bayer Advanced Tree & Shrub Insect Control, Merit) and acephate (Lilly Miller Ready-to-Use Systemic, Orthene). When properly applied, one application may provide season long control.
When using any chemical treatment on plants, it’s best to apply the product during early morning or late evening under cooler temperatures but never during the heat of the day or when the plant is in full sun. And always follow instructions on the pesticide label concerning mixing, application and safety precautions.