I need a natural way to kill ants around my banana trees.

http://homeguides.sfgate.com/dish-soap-around-fruit-trees-prevent-bugs-63220.html

equal parts sugar and borax, or corn meal

Dawn dishwashing liquid with water. Just mix three parts water one part dawn and spray the area daily for several days. Works great in the house too!

Terro makes various ant traps. The active ingredient in it is borax I believe.

Food grade Diatomaceous Earth. You can buy it at any farm supply store. I even use it on fire ants!

All ants can be killed with cornmeal. We were desperate and tried everything including poison and bait and nothing worked. Then an old timer told us about cornmeal. It worked! Place cornmeal around your trees. You may need a second application if the cornmeal gets taken away and there are a few ants still about. WE use Jiffy because it is sweet and they take it to the nest and kill the colony. I keep Jiffy in my pantry esp. in spring as new colonies will move in every spring. I seldom have to apply it a second time in the spring unless it rains before it is all taken up. Ants cannot digest it and it kills them, the queen, and all in the colony. It is safe for children, pets, and then environment. The best thing is it works!!!

cornmeal works pretty good for me

I will try it. Thanks

Some ideas here. Be careful not to cause harm to your garden: https://www.hometalk.com/diy/outdoor/pest-repeller/quick-dyi-sweet-bait-to-treat-and-get-rid-of-your-ants-18515410