Lace bugs (azalea and chrysanthemum lace bugs)

About

Lace bugs are flat insects about 1/8 inch long whose clear, net-veined wings look like lace. The azalea lace bug, native to Japan, is a major pest of azaleas, and the chrysanthemum lace bug feeds on mums, asters, goldenrod, sunflowers and their relatives (NC State, Oregon State).

Spotting it

Damage

Adults and nymphs suck sap from leaf undersides, leaving pale stippling on top that can bleach leaves almost white or bronze. Dark, varnishlike specks of excrement under the leaves are a giveaway (NC State, UC IPM). The harm is mostly to looks; Oregon State says azaleas tolerate up to 14% leaf damage without losing growth.

How to find it early

Starting in late winter or early spring, check new leaves about once a week for the first pale specks (UC IPM). NC State says the spring generations do the most damage to azaleas. Turn leaves over to find the dark, spiny nymphs and black specks.

When

Spring through fall; on azaleas the spring generations do the most harm.

Life cycle

Azalea lace bugs spend winter as eggs tucked into the leaf along the midrib and have two to four generations a year (Oregon State, UMass). Chrysanthemum lace bugs spend winter in dry leaves, grass clumps and other sheltered debris (NC State).

What to do, gentlest first

Start at the top. Sprays are a last step; always read and follow the product label.

1. Site and choose azaleas with care Prevent

   In the East, azaleas in sun, especially afternoon sun, are about twice as likely to be infested, so UMass suggests partial shade; in the Pacific Northwest, Oregon State says shade-grown azaleas suffer more. 'Micrantha' and native azaleas such as Rhododendron atlanticum, R. arborescens, R. canescens and R. periclymenoides resist lace bugs (Oregon State, UMass).

2. Hose off nymphs By hand

   Spray leaf undersides with a strong stream of water to knock off nymphs (UC IPM).

3. Protect natural enemies Natural enemies

   Lacewings, lady beetles, minute pirate bugs, predatory plant bugs, spiders and tiny wasps that attack lace bug eggs all help (Oregon State, NC State).

   Natural enemies may not prevent damage on their own (NC State).

4. Insecticidal soap or horticultural oil Organic spray

   Spray leaf undersides thoroughly when nymphs have just hatched; Oregon State reports up to 90% control with good coverage. Eggs inside the leaf are protected, so check again and repeat for the next hatch (NC State).

   Soap and oil work only on contact. Oil can harm bees it hits for up to about 3 hours (PNW 591), so spray when bees are not on the plants. UC IPM advises against long-lasting sprays because they harm pollinators and natural enemies, and UMass advises spraying azaleas after bloom. Some guides list neonicotinoids; they harm pollinators, so skip them. Read and follow the label, including its pre-harvest interval if you eat any part of the plant.

Garden friends that go after it

Brown lacewings, Green lacewings

Protect these helpers: skip broad sprays when they're around.

Plants it goes after

Aster, Azalea, Chrysanthemum (garden mum), Goldenrod, Hackberry, Japanese pieris, Linden, Mountain laurel, Oaks (white, red and pin oak), Rhododendron, River birch, Sunflower, Sycamore

Pressure by region

The azalea lace bug was first found in New Jersey in 1915, spread through the mid-Atlantic and Southeast, and reached Washington in 2008 and Oregon in 2009 (Oregon State). If you find it in a new area of the West, report it to your state department of agriculture. UC IPM lists more than a dozen lace bug species in California. Other ratings are estimates.

Ratings come from extension sources where available; some are estimates, as noted above.