Many small, black, varnishlike spots of excrement on the underside of leaves and discolored foliage are evidence of lace bug infestation. Eggs, nymphs, and adults all may be on a plant at the same time. Both adults and nymphs suck sap and cause leaves to be off-colored, speckled, and yellowed and to drop.
Lace bugs are small, broad, flat insects with clear, lacelike wings.
Ornamental and Lawn Pest Control .