Both azaleas and sycamore are susceptible to damage caused by insects called lace bugs. Damage results from the insect sucking out cell sap, resulting in a mottling of the leaves. The black tar spots are actually the insect’s excrement.

Control on sycamores may be impractical if the trees are large. If no action is taken, the trees will defoliate early, but no permanent damage will result. Azaleas should be sprayed with an appropriate insecticide if more than about 15% of the foliage is damaged. Azaleas growing in full sun are more frequently attacked by this insect than azaleas in the shade.

More information on lace bugs and their control can be found here: http://edis.ifas.ufl.edu/mg326