This insect sucks sap from the needles and can cause honeydew and sooty mold problems to be present in and under your Norfolk pine.
Scale insects tend to be cyclic in their populations. Normally, natural enemies of this scale will slowly, but surely, colonize and bring the population down. A normal, healthy tree can withstand a moderate scale problem while sustaining insignificant injury. Therefore, I would suggest you water and fertilize the tree to maintain health and vigor, and let nature reestablish a balance. Should the scale population persist to the point where there is visible injury to the tree, i.e., yellowing, dying and some defoliation of needles, one spray application of a summer oil will help suppress the scale insects to manageable levels. Use spray oils according to label rates and directions to avoid injury to the tree.