I've kept indoor bonsai for about 17 years and have never seen scale
indoors. In fact I've never seen anything on them other than about 3
instances of fungus knats after bringing them inside in the fall.

The only scale I've seen on bonsai was on a cork bark chinese elm and a
plum.

Alan
=F8 critters allowed

Blue Mountain Bonsai
Ontario, Canada
Zone 6