Azalea lace bug

What is azalea lace bug?

Azalea lace bug is a tiny insect native to Japan. Adults and nymphs feed on the undersides of azalea leaves with piercing, sucking mouthparts. Feeding sucks out leaf cells, which shows up as white to yellow speckles on the top of the leaf.

As feeding builds, leaves look bleached or bronzed. UMass says plants in full sun are often hit hardest and heavy infestations can kill them. NC State says the spring generations do the most damage.

There are two to four generations a year depending on climate (four in Maryland). The insect spends winter as eggs tucked into the leaf, so early spring is the key time to catch the first generation.

Signs and damage

• Fine white to yellowish speckling (stippling) on the top of azalea leaves
• Leaves that look bleached or bronzed when feeding is heavy
• Shiny black, tar-like spots of excrement on leaf undersides
• Small lacy-winged bugs and spiny black nymphs under the leaves
• Worst damage on plants in full sun

Azalea lace bug identification: what to look for

• Adult: About 1/10 to 1/8 inch long. Clear, lacy, cream-colored wings held flat over the back, with black or brown patches, and a hood over the head.
• Larva: Nymphs hatch nearly colorless, then turn black and spiny as they grow.
• Eggs: Inserted into the leaf along the midrib on the underside and capped with a hard brown, varnish-like drop. Up to 90 eggs on one leaf.
• Damage: White-yellow stippling on top of leaves, bleaching or bronzing, and black excrement spots underneath.
• Timing: Monitor from late April through summer. Spring generations do the most harm.

Life cycle

Spends the winter as eggs inside the leaf, under a hardened cap. Nymphs hatch in spring, molt several times, and become adults. Speed depends on temperature. There are two to four generations a year, with at least two in North Carolina and four in Maryland, so all stages can be present through the summer.

When to look: Start checking leaf undersides in late April and keep checking through summer. Look closely at new spring growth for the first signs.

Azalea lace bug look-alikes

A few things get mixed up with it:

• Spider mites: Also cause stippling, but NC State and the University of Kentucky note spider mites don't leave the black excrement spots lace bugs do.
• Thrips: Thrips also cause pale feeding spots, but NC State says lace bug injury is coarser than thrips injury.

How to control azalea lace bug

Cultural control

• Plant azaleas in partial shade; plants in full sun suffer more damage (UMass), and UC IPM says azaleas in partial shade get less lace bug damage than those in exposed sites.
• For new plantings, consider azalea species reported as resistant. UMass lists Rhododendron atlanticum, R. arborescens, R. canescens, R. periclymenoides and R. prunifolium as showing resistance.
• A varied landscape with more plant types supports more natural enemies, which can lower lace bug numbers (UMass).
• Check new spring growth for the first damage.
• The University of Kentucky suggests tapping suspect leaves over white paper to check for lace bugs, and says a strong jet of water can knock them off.

Biological control

• Tiny parasitic wasps attack the eggs, and the azalea plant bug and other predators feed on lace bugs.
• These natural enemies often don't prevent noticeable damage, especially in sunny spots.

Chemical control

NC State says early spring treatment may keep later generations low, since eggs are protected in fall and winter. Insecticidal soap and horticultural oil kill nymphs and adults (not eggs) on contact, leave no residue, and are easier on natural enemies. NC State names imidacloprid as a systemic applied to the soil, and UMass lists other systemic and contact active ingredients. Apply after bloom and when pollinators are least active. Use only products labeled for this use; the label is the law. Pesticide work for hire needs a licensed applicator; see our pesticide applicator license guide. Muthler Landscaping does not spray or apply pesticides.

Use only products labeled for this pest and this site; the label is the law. For trees, work with an ISA Certified Arborist. If you hire someone to apply pesticides, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Prevention

• Site azaleas in partial shade rather than full sun; the University of Kentucky says shaded azaleas have fewer lace bugs because natural enemies are more common there.
• Choose azalea species reported as resistant where they fit.

When to call a pro

Call a licensed pesticide applicator if large azalea beds are badly bleached year after year. Your Penn State Extension county office can help confirm lace bug versus mites.

Related guides: Tree database: mature size and planting distance · Pennsylvania tree identification · Firewood rules by state · All pests and diseases

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