Lace Bugs! Those speckled leaves on your rhodies and azaleas are usually a sure sign of lace bugs. Lace bug damage is first noticed as yellow spots on the upper leaf surfaces of affected plants. That’ because lace bugs damage plants by inserting their piercing-sucking mouthparts into the underside of leaves and sucking plant fluids. They kill surrounding cells as they feed causing the yellow spots to appear on the upper sides of the leaves. Heavy infestations cause leaves to brown and drop prematurely, which reduces growth or kills the plant.
Look at the undersides of leaves to detect active adults during the summer months. Turn a few leaves over and look for lace bugs with a 10 to 15 power hand lens or shake an infested branch over a white sheet of paper. The insects will fall off and may be more easily seen than on the foliage. The adults are 1/8-inch long with clear, lace-patterned wings. The transparent wings are held flat on the back. Their wings are lacy with two grayish-brown cross-bands connected in the middle. The adults have highly ornamented wings and a hood-like structure covering the head. The entire surface of the insect is covered with veins that look like lace.
Lace bugs are common pests of azalea, rhododendron, sycamore, broad-leaved evergreens and many deciduous trees and shrubs. Plants that attract lace bugs should be monitored early in order to determine if an infestation is building.
Elimination of the first generation of lace bugs is necessary if visual damage is to be avoided. Existing spotting and yellowing of leaves will not disappear once the lace bugs have been controlled. The undersides of leaves will also have brown splotches. Most lace bug infestations occur in bright, sunny areas. If you plant lace bug-susceptible plants such as azalea and rhododendron in shady areas of the landscape, lace bugs are rarely a problem. One effective control method is simply spraying down infected plants with a hard jet of water from a hose in the spring. This will dislodge the young nymphs as they hatch in the spring. The tiny nymphs often die before they can find their way back to suitable leaves.
Insecticidal soaps and oils are usually adequate if they contact the nymphs directly. Additional applications may be needed to control nymphs hatching out of late-laid eggs or if re-infestations occur from surrounding landscapes. Make applications as soon as the eggs hatch in the spring, usually mid to late-May. Monitor the plants and repeat applications if re-infestations occur. If plants are repeatedly attacked, consider moving them into the shade.