Azalea lace bugs can be a very destructive pest in home landscapes. Lace bugs feed with piercing-sucking mouthparts during both the nymph and adult life stages. The resulting damage appears as a grayish cast on the azalea’s foliage.
Lace bugs can be managed using several methods. The most effective preventative measure is growing healthy plants in an optimal location. Azaleas grow best in the morning sun with afternoon shade. Azaleas in full sun will become stressed and secrete compounds that lace bugs can detect, enabling them to target weaker plants. Choosing the right planting site and maintaining proper fertility based on recommendations provided by a soil test can go a long way in preventing future problems.
Several natural enemies, including parasitic wasps, predatory assassin bugs, lacewing larvae, lady beetles, jumping spiders, pirate bugs, and mites attack lace bugs. Avoid using broad-spectrum insecticides and plant native perennials to attract beneficial insects into the landscape naturally. For more information, see Attracting Beneficial Insects.
Insecticidal soap and horticultural oil sprays are extremely effective at controlling lace bugs. However, these products must directly coat the lace bugs’ exoskeleton to suffocate them. Soap and oil sprays have no residual effect, so beneficial insects are not harmed once the spray has dried.
Only use synthetic chemical controls on lace bugs as a last resort. The two basic types of chemical insecticides are systemic and non-systemic.
Systemic pesticides are usually taken up by the plant’s roots and distributed throughout the plant’s tissues. When the insect feeds on the treated plant tissues, it ingests the product, thus killing it. Systemic insecticide products effective in controlling lace bugs contain the active ingredients imidacloprid and dinotefuran. The active ingredient is listed on the label, usually toward the bottom in small print.
Non-systemic insecticides work by killing insects that come into contact with the chemical during or after application. Products with the active ingredients organophosphate (malathion) and pyrethroid (bifenthrin and permethrin) are very effective in controlling lace bugs. However, these chemicals also kill or repel natural enemies and other beneficial insects. Always read, understand, and follow ALL label directions before using a pesticide.
For more information on this and other insect problems on azalea, see HGIC 2051, Azalea & Rhododendron Insect Pests.