This past week more than a dozen specimens of Pieris japonica were received badly infested with lace bugs. If you have this shrub in your garden, better check it immediately.
Pieris japonica - also called Japanese andromeda and lily-of-the-valley shrub - is a beautiful evergreen plant when in good health.
Lace bugs feed by sucking sap from the underside of the leaves. Injured foliage becomes mottled with grayish blotches. Blanched and yellowed leaves drop from the plant; then twigs and small branches die.
Adult lace bugs are tiny (about an eighth of an inch long) and lace-like in appearance. Except for size and lack of wings, the nymphs (young) resemble the adults. Both feed on the plant.
Virginia Tech and University of Maryland specialists recommend spraying with Sevin for control of lace bugs. Directions on the label for mix and application should be followed closely. It's important to spray the undersides of the leaves too, because that's where the insects feed.
Do not spray unless your plants are known to be infested. Spray during late afternoon, because Sevin kills bees that help pollinate our garden plants. The bees usually are active during the morning and early afternoon.
The damage that has been done by lace bugs will not be corrected by spraying. Leaves that have been damaged will never regain good color, and sooner or later will drop off. If the plant is fairly vigorous, new leaves will appear. If not, the plant will die slowly.
To prevent a build-up of lace bugs on vulnerable plants, it's a good idea to check them about once a month with a magnifying glass.
Evergreen azaleas, mostly Hinodegiri and Kaempferi varieties, are also vulnerable to attack by lace bugs. The andromeda lace bug does not attack azaleas, and the azalea lace bug does not attack andromeda even when the plants are growing side by side. They're very similar in appearance, and treatment for control is the same.
The insects overwinter in the egg stage on the leaves of infested plants. Usually the overwintering eggs are at the bottom of the leaf. Those of the summer generations are on new foliage at or near the top of the plant.