Pest description and crop damage Overwinters in egg stage. Eggs are laid in the midrib on the underside of leaves. A new introduction to the PNW, little is known about the phenology of azalea lace bug in this region. Azalea lace bug eggs first hatch in early summer, with 2-3 generations in the PNW likely. Nymphs, the young immature lace bugs, are nearly translucent and light yellowish-green when small. As they age, they darken and become spiny. The adult nymphs are around 0.25 inch long, with wings that are slightly colored with white and black patterns in a window pane effect and quite sculptured. The head capsule is round and swollen-looking from the side.
Lace bugs have piercing/sucking mouth parts. The initial damage shows up as light yellow stippling on the surface of the leaves. Higher populations can cause more severe damage on azaleas, causing the leaves to turn nearly white. On rhododendrons, severe damage may look like iron chlorosis with yellow leaves and green veins. Lace bugs leave small black fecal spots on the underside of leaves. Exuvia, or cast skins, are also often present.
There are a range of predators that feed on azalea lace bug including azalea plant bug, tree crickets, earwigs, green lacewings, minute pirate bugs, and spiders. A Rutgers publication mentions one nursery study investigating augmentation with green lacewing larvae against newly hatched azalea lace bug nymphs resulted in 79-97% control.
Drought stressed plants are more susceptible to lace bug attack. Azaleas in the sun are reported to be nearly twice as likely to be infested. There are azaleas that show some resistance to azalea lace bug. High pressure water applications directed at leaf underside may dislodge the wingless nymph stages.
Insecticidal soaps and oils must directly contact the insects to control them and are most efficacious on newly hatched nymphs and can have high levels of control if used correctly. Horticultural oil can also smother the egg stage. Neem-based products act as anti-feedants, insect growth regulators, and repellants. Early season control is very important with these tools.
The egg stage is embedded in the plant material and thus protected from most control (except for horticultural oils). Most of the remaining chemical options act either as contact insecticides such as the pyrethroids or carbaryl or have systemic activity such as acephate or the Neonicotinoids. Contact insecticides and some of the systemic insecticides may have a detrimental impact on beneficial insects. Timing of the neocicotinoid insecticides generally is either a foliar application shortly before the egg hatch (6-8 weeks) or applied as a soil drench in the late fall.
For more information
Johnson, W.T. and H.H. Lyon (1991), Insects That Feed on Trees and Shrubs, 2nd ed., Cornell University Press (p. 424).
PNW Nursery IPM: Azalea lace bug (http://oregonstate.edu/dept/nurspest/azalea_lace_bug.htm)