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Lace bugs are common pests of azalea, rhododendron, sycamore, broad-leaved evergreens and many deciduous trees and shrubs. 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. Description: Adult lace bugs are about 3 to 6 mm (1/8 to 1/4 inch) long with a netlike pattern on the wings, which are dotted with brown and black. The immature stages, or nymphs, are similar except they are smaller and often have spines. The eggs, although small, are easily distinguished by their elongate and cylindrical shape. They resemble small, black smoke stacks attached to the undersides of the leaf.
Life Cycle: Lace bugs can be divided into two groups - those that attack deciduous trees and shrubs and those that attack evergreen shrubs. Lace bugs which attack deciduous plants spend the winter in the adult stage by hibernating on the plant under bark or near the plant in leaf litter. Lace bugs which attack evergreens overwinter in the egg stage attached to the leaves. The hawthorn lace bug is one species which attacks deciduous plants. The adults hibernate under loose bark of their host plants as well as among leaf litter. They become active in early to mid-May and return to the new leaves. The females soon begin to lay eggs along the larger veins on the lower leaf surface. The females may lay eggs for a considerable time, often extending into June. The eggs hatch in a couple of weeks, and the nymphs cluster together and feed. Each nymph sheds its skin (molts) five times before the adult stage is reached. Growth to the adult stage usually takes three to four weeks. Peak numbers of this pest are usually present in July. Only one generation occurs per year. Related species of lace bugs such as the oak, sycamore and hackberry lace bugs have two and occasionally three generations in a summer. The azalea lace bug is an example of a lace bug which attacks evergreens. The azalea lace bug overwinters in the egg stage. The eggs are partially inserted into the leaf tissues along the midvein and are covered with the resin-like excrement of the female. The nymphs hatch in the spring, usually mid-May. They feed in small groups on the under surface of leaves and molt five times before becoming adults. The adults mate and lay eggs for a second generation by mid to late-July. Often there is a third generation in the late summer and early fall. The andromeda and rhododendron lace bugs have similar life cycles. Damage: Lace bug damage is first noticed as yellow spots on the upper leaf surfaces of affected plants. Lace bugs actually feed on the undersides of leaves with their piercing-sucking mouthparts, but because they kill surrounding cells as they feed, they cause the yellow spots to appear on the upper sides of the leaves. The first yellow spots that appear are very similar to mite damage, but the spots made by lace bugs are much larger. When feeding damage becomes severe, the leaves take on a gray blotched appearance or can turn completely brown. As lace bugs feed, they produce brown varnish-like droppings that spot the underside of the leaves. These droppings further distinguish lace bug damage from mite damage. When large numbers of lace bugs are present, cast skins can be found attached to the leaves. Control: 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. Cultural: Most lace bug problems occur in bright, sunny areas. Plant lace bug-susceptible plants in shady areas of the landscape. The azalea and rhododendron lace bugs are rarely a problem when their host plants are in a shaded understory. Syringing can also be an effective control method. Use a hard jet of water from a hose to 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. Biological: Encouraging the natural predators of lace bugs is important. Green lacewings, mites and assassin bugs all attack lace bugs and will generally keep a lace bug population in check, especially if host plants are sited properly. However, these predators often arrive after considerable damage has occurred. In order to conserve these beneficial natural predators, use syringing or insecticidal soaps or oils instead of standard insecticides. Chemical: Insecticidal soaps and horticultural oils are useful if they contact the nymphs directly. Be sure to cover the underside of the leaves where the nymphs are feeding. Additional applications may be needed to control nymphs hatching out of late-laid eggs or if re-infestations occur from surrounding landscapes. Several over-the-counter insecticides are effective in lacebug control, but soaps and oils are usually adequate. Be sure to check a product's label, as not all lace bugs or host plants are listed on each label. 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.
Adapted
from the Virginia Cooperative Extension and the Ohio State Cooperative
Extension, 1999.
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