I've used a product called "Terro Ant Dust" with great success. Think I found it at Menard's; bright orange cannister of powder - theory being dust it around the hill and the ants carry it in dessimating the colony (and rather quickly). Normally I try to avoid chemicals, but sometimes you just have to take action. I haven't had any major ant problems since destroying a big colony (maybe a third the size of yours) a couple of years ago with the Terro.

The little ants that tend to crop up in garden spaces can be moved along simply by disturbing the soil.

I had a really bad ant nest around the roots of a young crab apple. The tree was getting stressed, so early last fall I took drastic action. Bayer makes a granular insect killer that also works on ants. You sprinkle it on the area and water it in well. I have dogs so I kept it confinded to a small area then put a large-ish piece of flagstone on top of the soil where the poison was applied. I am happy to say that the ants are gone and the tree is doing much better this year.

janetpetiole, where did you purchase the Bayer granular at? We have trees with lots of ant as well being stressed, would like to give it a try.

I'm not sure where I got it, but it was probably Steins. I think the Bayer products are getting popular, so it might be easy to find. It's called "Multi-Insect Killer". It kills earwigs too - bonus.

I hate using pesticides, but I refuse to loose a tree due to ants.

aspertame, SUPPOSEDLY will do the trick as well...it's a grapefruit rind extract and is used by some on fireants. But not having any fireants here I wouldn't know how effective it is...:)