As per my last comment apply a topical insecticide recommended for control of mealy bugs. These guys are also vectors for plant diseases so you can get a cascade effect of trouble for your plant if you delay. Good Luck!

You need one based on insecticidal soap, the white stuff is a waxy substance which stops water from getting to the bug inside.

It's very good of you both to reply again to this idiot . . . many thanks!

Actually I was rather pleased to see your posting (not happy with the bugs) I asked last year for the id of a tree and as usual in this garden the label has disappeared. It is Styrax japonica like yours, so I can label it again.

Gardeners are always happy to help each other, Owdboggy!!