Hi bgli,
This is what I use :
- coffee for filters in coffee machines . Use it new from the pack, sprinkle that at the base of the tree in a layer and in the nest of the ants if you spot it.
- extinct lime from construction shops. Brush that on the trunk, base of low branches and around at the base of the trees and again on the nests of the ants. Lime, in the hole of rodents, seems to deter the rodents too.
Good luck !
Don't use chemicals now as your going to eat the figs soon. You'll use that come next Spring when the fruits are in standby stage.
You still have the mechanical way : wear gloves and rub the ants against the trunk. I do that sometimes when I'm getting reaaaally p*ssed.
PS: Of course after rain, you may have to add some more coffee or lime .
Extinct Lime so far has been the best method - That is the white wash that some people do use on the trunks of their trees.
As always with new things, try with a little bit first before going wild... That is what I did too . I used lime on a peach tree and the damn thing is still alive - I was looking for a new spot for a new fig tree ... LOL . Afterwards, I used it on one fig tree and now on all. So far none of the trees did complain .