Information from the University of Maryland Extension Landscape and Nursery IPM Report
In Maryland, spirea aphid (Aphis spiraecola) is active in May. Predators and parasites often collapse the populations as we move into June. In years of heavy populations, they can excrete a fair amount of honeydew on which sooty mold grows. This aphid is also reported on crabapple, apple, hawthorn, quince, and pear.
Control: If you must treat, try an insecticide with reduced or zero impact on beneficial organisms such as neem oil or horticultural oil.