Scale are insects that secrete honeydew and feed on plant tissue. Small infestation are easily controlled by hand removal or pruning. Larger infestations may require spraying with a dormant oil before budbreak or application of pesticides during the crawler stage. Although rarely a critical problem, if left uncontrolled scale may weaken the blueberry bush and predispose it to disease or abiotic problems. The photo below was taken in Poplarville, Mississippi of a wax scale.
More information on these types of scale can be found at NC State: http://www.ces.ncsu.edu/depts/ent/notes/O&T/shrubs/note13/note13.html Virginia Tech: http://pubs.ext.vt.edu/444/444-622/444-622.html and Florida: http://edis.ifas.ufl.edu/mg005