I had an ant infestation after the a party we had on the 4th. I use the method outlined in this article:
How to Kill Ants That Live on Orange Trees | Home Guides | SF Gate
I'm not sure if Borax can be used as a substitute for boric acid. I ordered the boric acid from
Amazon.com : 2 Pk, Boric Acid Roach Outdoor.
I added about a tablespoon of corn syrup to my last batch and it attracted ants immediately and killed them off within a couple of days. I've used this method around our fruit and orange trees also. The strategy is to create a mixture that does not kill the ants immediately. Instead, they carry it back to the nest to kill the queen. No queen=No colony.