White Prunicola scale is a scale that is most commonly found on Prunus spp. (stone fruits), particularly Prunus serrulata, the Japanese flowering cherry, Ligustrum spp. (privet) and Syringa spp. (lilac).  Injury to the plant results from the removal of plant juices. Larger branches and trunks are preferred but in severe infestations, smaller branches, twigs, and other plant parts may be attacked. Heavy feeding can result in branch dieback and complete plant mortality.  The scale is small and looks like a white powdery coating on the trunk and branches.  This scale is quite common in the landscape and is very hard to control.  If the infested plant is to be saved steps must be taken to reduce stress on the plant and control the scale population.  Information from Dr. Maurie Semel, Cornell Extension.