Did you notice off-color leaves on your broadleaved evergreens, such as azalea, rhododendron or Andromeda last year?  These popular landscape shrubs are sometimes attacked by lace bugs and their feeding damage results in small, yellow to brown flecks on the leaves. When there are many of these, the whole leaf, and even the whole shrub, can look off color from a distance.

Lacebugdamage.bugwood

Leaf discoloration caused by the feeding of lace bugs. Photo credit: William Fountain, University of Kentucky, Bugwood.org

What are lace bugs? They’re insects in the family Tingidae and have piercing and sucking mouth parts. They are small – the adults are only 2-3 mm in length. They are quite distinctive looking. Adults have flattened bodies with lacy looking wings that give them their common name. The species on broadleaved evergreens appear black and white. Nymphs are quite dark in color, up to about half the size of the adults, depending on their growth stage (instar) and are covered with dark spines.

 

It’s easy to miss these pests as the cause of leaf discoloration because the feed and reproduce on the lower leaf surfaces. They pierce leaf cells and suck out the juicy contents, resulting in cell death. So a lot of this type of injury due to a high population can result in reduced photosynthesis that in turn leads to poor plant health, leaf drop and reduced flowering.

Lace bugs that attack broadleaved evergreens overwinter in the egg stage. Eggs are laid in the leaves of the veins, mostly on lower leaves, and then covered by the female with a cement or varnish like material. Spring hatch occurs typically in May in the northeast. Nymphs begin feeding immediately and go through five nymphal stages or instars before becoming adults. Under favorable conditions, the entire life cycle may be completed in one month. Depending on lace bug species, there may be 2-4 generations per year in Connecticut.

To protect plant health and also to prevent unsightly discoloration of the leaves, monitor for lace bugs early in the season on susceptible plants, especially if they have evidence of injury from the year before. Nymphs and adults can be sprayed off plants with a strong stream of water or they can be treated with horticultural oil or insecticidal soap. Both of these products must coat the pests to kill them so thorough coverage of the leaf undersides is required. Inevitably, some individuals or eggs will survive so a second application may be necessary. Prevention of damage before it gets too severe is important because leaf discoloration will persist for a year or more.

Both azalea and rhododendron lace bugs are more likely to build up to high, damaging populations on plants in sunny locations. The Andromeda lace bug can cause a lot of trouble in both sunny and shady sites.

As mentioned above, there are a number of susceptible plants found commonly in northeast landscapes. The lace bugs have quite narrow host ranges as shown below:

               Lace bug species                                                          Host plants

Andromeda lace bug Japanese Andromeda, Leucothoe
Azalea lace bug Azalea and mountain laurel
Rhododendron lace bug Rhodendron and mountain laurel
 

By J. Allen