Last year i had some ants inside my rippened figs,not all of them just a few.

My question is there any way to keep them from climbing up and into the half whiskey barrels that i grow the tree's in. I would not like to use anything harmful to the fig tree's. There about 4 years old and i have 5 of them and it looks like i will have many figs this year as they are sprouting on most of the branches now and i would like to put something to protect them before they start to get ripe.

Thanks

Marty