Here's an organic treatment which doesn't bring toxins into your space. It's slow acting , but it worked great for an infestation we had in the kitchen. I can't guarantee it will work for all species, but it is a simple recipe: add baking soda and fine (confectioner's) sugar in equal amounts and mix well. Add a little water to make a paste, then put it in a container on the ground near an ant mound. In a few hours, you will see ants clustered in the mix. The way it works is simple: the ants are attracted by the sugar, and they ingest the baking soda as well, which causes gas in the ant's gut. Ants have an exoskeleton, which doesn't allow them to vent the gas, so they literally explode, in a manner of speaking. For really stubborn infestations, a second application may be necessary. Give it a couple of weeks to work.
My biggest problem with ants outside is when they have a colony in plant containers. This can affect the growth of the plant; my experience is that those plants just don't do as well. The above mixture will work, but if you are in a hurry to get rid of them, just get some ant poison of your choice, move the plant, spray the ground or surface where the container was, then place the container in the same spot. It's worked well for me.
