2 Answers

Sprinkle Diatomaceous Earth, which is granulated fossilized remains of diatoms, a type of hard-shelled algae, around the base of the nest. The material is razor sharp. The sharp edges of the granules will injure or kill the ants that crawl over it.

Another deterrent is chili pepper flakes or powder sprinkled around the periphery of the mound.

Remember, when you apply anything to the garden, you are affecting the entire community of insects, many of which are beneficial.

Read more of this article here>>http://articles.chicagotribune.com/2008-08-15/entertainment/0808130729_1_carpenter-ants-organic-matter-chicago-botanic-garden

If you get the food grade , put a teaspoon in water a drink . Tastes a little like clay, but good for you. Works on intestional gut worms in people too. But only consume food grade diatomaceous earth.