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If you have azaleas or lantana in your garden, you have probably dealt with lace bugs. These tiny insects can cause unsightly damage to azaleas, lantana and mountain laurel. I knew it was time to talk about this annoying critter after four people brought lace bug damaged lantana to our remote broadcast of GardenLine at Cornelius Nurseries.
Lace bugs cause damage by essentially sucking the life from the lantana or azalea through their siphon-like mouth. 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. More specifically on lantanas, the first noticeable symptom is the partial or complete absence of flowers on otherwise healthy plants. The discoloration on lantana, as opposed to azaleas, can give new growth a scorched appearance.
If you notice spotted discoloration on azalea or lantana leaves, turn the leaves over. If the discoloration is being caused by the lace bug, you will notice tarry black spots caused by the insect's frass (frass is what entomologists call insect poop) and the shed skins of growing lace bug nymphs (what entomologists call teenage insects). The undersides of the leaves may also have a rusty appearance, and you may actually find the culprit: azalea lace bug 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 in length. With good eyes or a magnifying lens they appear to have spines sticking out of the sides of their bodies.
Lantana lace bug adults are oval, brown and do not have the characteristic 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 in length. Lace bug nymphs, like azalea lace bug nymphs, have spines sticking out from the sides of their bodies and no wings. They appear less elongated than the adult lantana lace bugs.
 
Valuable plants that are susceptible to lace bug damage or that have a history of lace bug infestation should be inspected in the early spring for the presence of lace bug 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 lace 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 available insecticide will kill lace bugs, especially those that have a systemic property -- Acephate, Malathion, Bayer Advanced Garden, Tree and Shrub Insect Control, almost any Rose and Flower insect spray and 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 choice. Most systemic rose and/or azalea foods contain Disyston. Bayer has one with Merit.
The systemic rose food is better for the lantana. It is applied around the base of the plant, taken up by the roots and moved through the plant's vascular system. Because this insecticide must be absorbed by the roots and moved throughout the plant, it may take a couple of weeks to see results. On the plus side, you may get season-long control of lace bugs from a single application. This insecticide also works well controlling aphids and some scale insects (wax scales and other soft scale) and is probably the best insecticide available to homeowners for controlling whiteflies. Since this insecticide 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. This means plant foliage must be thoroughly sprayed with particular attention to getting spray on the lower surfaces of leaves (as well as flowers and flower buds in the case of lantana) 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.
Until next issue, here's to
Great Gardening from the GardenLine, heard
exclusively weekend mornings from 8 to noon
on Talkradio 950 KPRC.
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