The problem is on a ficus (scale that I would like to eradicate before the
trees come indoors).

Orthenex is very effective against scale. Use as directed about three times at
weekly intervals. However, you will never get 100% cure. The scale may well
recur next year, especially if the plant goes outdoors for the summer. This is
one case where a preventive spray may be indicated, if you know the tree is
likely to get scale every summer.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)