Sometimes there is no choice if you want to save a tree and have to use Imidacloprid as a last resort. I have a huge Magnolia tree that's over 60 years old now that had a severe infestation of scale bad enough that it would have killed the tree if left untreated. Imidacloprid has to be applied in early spring to get the magnolia scale while they're still soft, once they harden up into the white blobs it has no effect. But I waited until after all the flowers dropped before applying to avoid poisoning any pollinators, and that was still early enough to work.
It would have been impossible to get any type of spray everywhere on a 50' x 50' tree with multiple trunks to finally get rid of the scale any other way.
