periskiopsis graft with with substance

[art west co]

Hello. I have a periskiopsis graft that has developed a white substance. Does anyone know what it is and what would be the best course of action to treat the plant? Here is a picture.

[HP22B]

Looks like the same thing that happens to my older stocks. For me it is typically lifting of the outermost tissue layer which causes it to look bubbled/cracking. Probably nothing to worry about, I think it comes with age.