Is there such thing as a safe systemic insecticide for mealybugs?

[Foogoo]

I have a moderate to bad infestation of mealybugs on all my phals, my fault for not identifying them sooner. So far, I've been using alcohol and Safer Soap, it's working but they keep returning.

I'd like to stay away from strong insecticides such as imidicloprid after inadvertantly killing my local bees from using it outdoors last year. Is there something that can effectively control my mealybug problem?

EDIT: I just remembered something I read in another thread - how high does the temperature have to be kill mealybugs? Has anyone tried controlling them using natural or artificial heat?