@ Fred...Try using Sevin (powder form)...or even Boric Acid. Lay a circle of the powder around the ant hole so they track it when they go down into the ground. Unwittingly they will track it back to the nest...and...kill the colony. When I get aphid investations on my citrus it's due to ants living in the soil around the trunk and I have gotten rid of the nests by doing as I mentioned..... After a while...no more problem!
