If spinosad is legal where you are, I would use a bait containing it near each mound.

Thank you, but what is spinosad? Is it tradename of some chemical or what? Did not find it in vocabulary.

Hi Tugbrethil, sorry, one "bad" somment: I noticed you are from Arizona. Are there gardens? LOL. Just joking.
It must be hard work there to found and keep the garden.

any leading ant powder will rid you of these pests quit quickly .

Hi Katarina, my view has always been that wildlife has to go somewhere - this planet is not just for us..............and as with any eradication programme such as the badgers if you break up colonies the situation multiplies (the survivors set up numerous other colonies)
Any chance you can work round them - best of luck.

i agree john

Well, thank you John very much for your fundamental ecologic view. I agree, each living creature has right to live on the planet. That is why I am not using chemicals in my garden. On the other side, ecology is about balance. Those ants lived in my garden also before and hope they will after me. But now they are overpopulated as they made large colonies. And I have to do with it something. I am looking forward to some advice from good gardeners. But thanks.

I recommended spinosad, Katarina, because it is safe for people, pets, and wildlife, but it's relatively new, and I'm not sure which countries have approved it or not.
Yep, we do have gardens here, but we need to spend so much money on soil conditioning, fertilizer, and water, that we grow vegetables for therapy, not to save money! : )

Thank you, Tugbrethil.

Oh Tug, I know exactly what you mean!!