Hello,

Is there any way you can send us some pictures of the white scaly growth? It mostly likely is an insect, White Prunicola/Peach Scale, but without pictures we cannot say for certain. Pictures of the scale insect, as well as control recommendations can be found in the aforementioned link. 

Please note that some wood decay fungi, as well as lichen, can also appear on the surface of bark and be mistaken for an issue.

Marie