If you spot just one ant in your fig tree, it means that you already have a problem. Ants usually travel in large numbers and for every single one you find, there are hundreds more that you haven't spotted. Spraying your tree with pesticides will definitely put an end to your ant troubles, but it will render all your figs inedible. Fixing this problem organically is the safest way to save your tree and remove the pesky invaders.
Wrap tape around the base of the tree with the sticky side facing out. As ants begin to trek up to your figs, they will not get very far. Remove the tape as often as needed to dispose of the immobile ants.
Place a piece of fruit or some other type of food attractant on a pile of dirt or on top of a flower pot filled with dirt. When many ants are present and swarming the bait, pour soapy water all over them. Dish soap is very bad for ants, but will not harm anything else in your yard. Use a long-handled shovel to stir the soapy water around into the soil and kill as many ants as possible. Repeat this process as many times as you would like, to see a significant decrease in the ant population.
Sprinkle dry grits around the base of the tree to distract the ants with the prospect of a free and easy-to-reach meal. They will take this back to their nest and feed it to the others. The grits will expand in their stomachs and kill them quickly. If the queen eats it, she will die and the colony will be forced to move on.
Locate their home and pour a pot of scalding water into it. This may take a few applications, but ants will soon understand that they are not welcome.
Take a long-handled shovel and dig a hole into their ant hill. Be sure to wear gloves and long sleeves. Tuck your pants into your boots and be advised that the ants are not going to be too happy about this. Drop a piece of dry ice into the hole and cover it back up. This will kill many ants and force the survivors to move on.