... because of this outstanding presentation on scale (Diaspididae). From it, I lifted this anatomical drawing.
Hopefully, Tim will weigh in on the details, but it looks to me like the thing breathes through its head and not from the juices of the plant. That means that his idea of an anoxic chamber would do the trick as would a hypobaric chamber. No oxygen = no scale, 100%, all dead, gone, gone, gone.