If you have azaleas or lantana , you have probably encountered lace bugs. These tiny insects can cause unsightly damage, and also affect mountain laurel.
They essentially suck the life from the plants through their siphon-like mouths. In azaleas and lantana, lace bug damage first appears as spotted discoloration or bleaching on the upper surfaces of leaves. In severe cases, leaves can be almost completely bleached and may even drop from the plants. On lantanas, the first noticeable symptom is the partial or complete absence of flowers on otherwise healthy plants. The discoloration can give new growth on lantana a scorched appearance.
If you notice spotted discoloration on azalea or lantana leaves, turn the leaves over. If the discoloration is being caused by lace bugs, you will find tarry black spots caused by the insect's frass (what entomologists call insect poop) and the shed skins of growing lace bug nymphs (what entomologists call teenage insects). The undersides may also have a rusty appearance, and you may actually find adults and nymphs.
Adult azalea lace bugs are slightly longer than an eighth of an inch and are somewhat rectangular in shape. Their wings and body coverings have a characteristic lacy appearance that can be seen with the naked eye or with a low-power magnifying lens. Nymphs bear little resemblance to their adult counterparts, and an inexperienced observer may not recognize them as lace bugs. Nymphs range in size from one-sixtieth to one-fourteenth of an inch long. With good eyes or a magnifying lens, they appear to have spines sticking from their sides.
Lantana lace bug adults are oval, brown, and do NOT have the lacy body covering and wings. They are narrower than the azalea lace bug. Adults range in size from slightly over one-eighth inch to slightly over one-sixth inch long. Lace bug nymphs, like azalea lace bug nymphs, have spines sticking from sides of their bodies and no wings. They appear less elongated than the adult lantana lace bugs.
Valuable plants susceptible to lace bug damage or which have a history of lace bug infestation should be inspected in early spring for the presence of adults and newly hatched nymphs. Inspect plants every two weeks during the growing season. Lantana infested by lace bugs need to be treated with an insecticide, or they will stop blooming until the bug population naturally declines. Without treatment, infested lantana may go a month or more with few or no blooms. On azaleas, dislodging lace bugs from infested plants with a strong stream of water may be sufficient to disrupt populations early in the season. It will probably take several soakings, and even this may not be enough.
Almost any insecticide will kill lace bugs, especially those with systemic properties — like Acephate, Malathion, Bayer Advanced Garden, Tree and Shrub Insect Control, or Sevin. If you don't have a serious infestation, but would like to prevent any possibility of lace bug damage, feeding the azaleas or lantana a systemic food is also a good idea. Most systemic rose and/or azalea foods contain disyston. Bayer has one with Merit.
Systemic rose food is better for lantana. When applied around the base of the plant, it is taken up by the roots and moved through the plant's vascular system. Though it may take a couple of weeks to produce results, you may well get season-long control from a single application. This insecticide also works well to control aphids and some scale insects (wax scales and other soft scale), and it is probably the best insecticide available to homeowners for controlling whiteflies. Since it works within the plant, do not use it around vegetable gardens, fruiting trees or other edible landscape plants.
To be effective, sprays other than those with a systemic property must directly contact the lace bugs. Plant foliage must be thoroughly sprayed, with particular attention to the lower surfaces of leaves (as well as flowers and flower buds, in the case of lantana). That's where most lace bugs will be found. It may take more than one insecticide application to control the pests, so check your plants again in a week to make sure you have done a thorough job.