I, too, had an infestation of aphids and scales on some of my fruit trees and on a gardenia. Both pests were being farmed by ants. I treated the affected plants/areas with bifenthrin granules but the ants (they were crazy ants, BTW) just walked thru the bifenthrin; it never fazed them and they just kept on 'farming'.
Subsequently I tried using Imidacloprid granules around the base of the affected plants and watering it in per instructions for the product. That killed both the aphids and scales, plus when the ants 'discovered' that their 'farmed animals' were dying they moved to other non-fruiting, non-treated plants in the yard. When the Imacloprid's effect wore off the ants came back to my fruit trees and resumed 'farming'. Then when more Imidacloprid was re-applied the ants left again.
Eventually, after continued re-treating my afffected plants the crazy ants did give up and apparently moved elsewhere and I've had no further problems wth aphids and scales. I recommend using Imidacloprid.
Paul M.
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