jollygreen pimp:
Let me share with you a trick I use to keep ants away from my figs. I pour a wide band of insecticide completely around the base of the tree, including the base itself, double or triple the recommended dosage for ants. The stronger the solution the better because the chemical does not touch the fruit. My belief is that at the end of the day the ants retreat to their burrows and come in contact with the chemical. After a day or so there's hardly an ant to be found. Repeat as necessary. I've done this a number of times over the years, and it works!

Frank

A little powdered sugar mixed with Borax "detergent" and a few drops of water forms a paste you can put put on little pieces of cardboard/papercard. It has been an effective ant control for me. I put the little baits scattered around their trails they seem to favor.

Usually after 2-3 days i can remove the little cards with gunk (which hardens in the sun) and not see ants for a while.

Box of borax, $2, powdered sugar, $1...enough applications for years.

J.G.P., what you most likely have are cornfield ants. They will not eat or damage the corn, and may even control a few harmful insects. What they will do, however, is raise large numbers of aphids on the corn & any other nearby vegetation.

The aphids themselves can become a problem, if while being carried plant-to-plant by the ants, they spread disease. This is especially true of viral diseases like mosaic.

To control the aphids is very difficult without first killing the ants; if you spray all of the aphids on a plant, the ants will only bring more from their underground hatcheries on the corn roots. Personally, I disagree with the broad use of insecticides on or near food crops. What I recommend instead is the use of ant baits, placed under covers to prevent birds or animals from having access. These baits will kill the entire nest very quickly, and can then be removed & disposed of.

But provided that you are having no disease problems, the ants are causing no harm, and are only an annoyance... in which case, I would recommend doing nothing.