[efisakov]

I dust DE around my plants to deter slugs and ants (too many is too many). Works great. After big rain I reapply.
Spraying is best at the most humid times and the times of infestation. I agree with Bill, mixing DE with soap works great.

BTW there are some ants that are NOT that great in your garden:
"Some species of ants farm aphids, protecting them on the plants they eat, eating the honeydew the aphids release from the terminations of their alimentary canals. This is a mutualistic relationship. These dairying ants milk the aphids by stroking them with their antennae.[Note 1][22]
Some farming ant species gather and store the aphid eggs in their nests over the winter. In the spring, the ants carry the newly hatched aphids back to the plants."

I look at ants now differently. The once mentioned above were in my garden. I have witness exactly what they are talking about. Took pictures as well.