Baking Soda and Cornstarch
My mother once dumped baking soda on a fireant mound. The workers went nuts and the winged ants flew the nest. I've thought about trying it, but I'm afraid it would make my soil too alkaline and full of sodium...or that ant predators would be averse to it or get sick from it.
If the ants left for the reason I think they did (the powder was too fine for them to pick up or tunnel through like soil), I should be able to get the same effect with a different powdery substance. What about cornstarch? Would that ruin the soil? Would any animals be harmed by it?
(And yes, I know making the ants relocate doesn't eradicate them, but researchers say disrupting their workings helps give predators and native ants the advantage.)