For what its worth, I am down to less than two cents so I just throw in the
little that I have left:

A scary and little known fact here is that Brand names and their active
ingredient may vary from year to year, from country to county or from state
to state. There must be a good reason for this. It probably has something
to do with changing manufacturing guidelines and the laws applicable in
various jurisdictions where the chemical is sold. Anyway, the various
formulations; i.e. liquid, granular, powder, etc may also contain different
active ingredients as well as different "inert" ingredients but inert does
not mean it won't harm plants, applicators or bystanders under certain
situations.

If you have identified the insect you want to control as being "scale" then
the labels of brand names with active ingredients you find at your local
PesticideMart that control scale will list scale among the insects it
controls. Nowadays Pesticide makers seem to be using pictures of the
insects controlled by the brand name even as the reminds you to read it in
its entirety. Brand name X in California might not list scale as an insect
it controls but a bottle of brand name X in Virginia will. This might be
because they are different active ingredients but, and here's a scary
observation: Brand name X in both states might actually contain the same
ingredients but one jurisdiction does not approve it's use for scale in
over-the-counter residential type home garden applications so scale will not
be listed on the bottle that is sold there.

Almost certainly, whatever you use will require several timed applications
over several weeks. I suggest that you find two different chemicals that
control scale and alternate their application as part of a several week long
total application cycle.