Lace bug activity has begun in Delaware and a great way to minimize the damage they cause is to control first generation nymphs or the overwintered adults as they resume feeding. Hawthorn lace bugs feed on hawthorn, cotoneaster, quince, crabapple, mountain ash, and pyracantha. Azalea lace bugs tend to feed on evergreen ornamental shrubs and oak lace bugs feed on different species of oak trees. The first generation of azalea lace bugs nymphs is active from 240 561 [318 peak] GDD and the 50 peak of adults is between 2802 3418 GDD . Overwintering 50 hawthorn lace bug adults begin feeding in the spring at 196 472 [349 peak] GDD or when Lagerstroemia indica is at the leaf bud 50 break phenological stage. Oak, sycamore, and azalea lace bugs may have two to three generations a year.
Lace bugs are usually found on the underside of leaves and they suck out plant juices with piercing mouthparts. Their feeding also kills nearby cells causing yellowish flecks on the upper leaf surface which coalesce into large bronze-colored patches. High populations may damage plants enough to cause premature leaf drop. Small lacelike adults may be difficult to see; an easier method to verify the presence of this pest is the fecal matter, which appears as shiny black spots called tar or resin spots. Lace bug nymphs are not lacelike, but are spiny and usually dark brown to black.
Horticultural oil or insecticidal soap applications must contact the insects; thus spray the underside of leaves. Both of these products have low impact on the natural enemies attacking lace bugs. Heavy infestations may require the use of products such as acephate, carbaryl, cyfluthrin, imidacloprid and pyrethrin. Plants with a history of mite problems should not use imidacloprid as a treatment.
Azalea lace bug adult. Photo from Pest and Diseases Image Library, Bugwood.org.
Lace bug damage on azalea. Photo by Whitney Cranshaw, Colorado State University, Bugwood.org.Information from Brian Kunkel, Ornamental IPM Specialist, UD
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