The woolly apple aphid, Eriosoma lanigerum, is a cosmopolitan pest of apple. Historically, the solitary endoparasitoid, Aphilinus mali, has been considered the most important natural enemy of this pest, although its effectiveness varies considerably among geographic regions. Furthermore, woolly apple aphid populations often increase to damaging levels prior to suppression by A. mali. The role of predators in the biological control of woolly apple aphid is not well understood. In mid-Atlantic apple orchards, several species of aphidophagous hover flies are the most common predators of the aphid, including generalist and specialist species. Potted apple trees infested with woolly apple aphid were used in exclusion cage experiments to evaluate the role of predators in the suppression of colony development early in the growing season and in colony elimination later in the season. In concert with the exclusion cage study, destructive samples of woolly apple aphid colonies were taken from potted sentinel trees deployed in the same orchard for 2-day intervals each week and provided a measure of the relative abundance and species composition of the syrphids present throughout each experiment.