Lace Bugs Cause Problems for Azaleas and Lantanas

Mobile, June 16, 2003---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, rhododendrons and mountain laurel, according to Chazz Hesselein, an Extension horticulturist at the Ornamental Horticulture Research Center in Mobile.

Lace bugs cause damage by sucking through their siphon-like mouth. In azaleas, 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.

In lantanas, the first noticeable symptom is the partial or complete absence of flowers on otherwise healthy plants. Lace bugs can also cause spotted discoloration on the upper surface of leaves and in severe cases give new growth a scorched appearance.

If you notice spotted discoloration on azaleas leaves, turn the leaves over. If the discoloration is being caused by the azalea 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, Hesselein said.

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 bugs are more commonly found on the underside of the flower parts (or where flowers used to be) and on the undersides of newer leaves, Hesselein said. As with azalea lace bugs, infestations can also be confirmed by tarry black frass and the shed skins of lace bug nymphs. 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 -- Orthene, Malathion, Bayer Advanced Garden, Tree and Shrub Insect Control, Spectracide Rose and Flower Insect Spray, Lawn and Garden Multi-Insect Killer, horticultural oils, insecticidal soaps and Sevin.

To be effective, sprays 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.

“Horticultural oil and soap products are effective against many insect pests. They have very low toxicity to humans, pets and other animals, and, since they are only effective in their liquid state, once dry they are not harmful to beneficial insects,” Hesselein, said.

One other product -- Bayer Advanced Garden, Tree & Shrub Insect Control--contains a relatively new active ingredient, imidacloprid. 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.

Source: Chezz P. Hesselein, Horticulturist, Alabama Cooperative Extension System Ornamental Horticulture Research Center, (251) 342-2366.

Article in MS Word

Article in Text