It appears our four year old house was built on a fire ant nest. I have been putting diatomaceous earth on it and recently I put orange oil also. The nest is bigger than ever - help!

From what I understand, it is best to drench the opening with fire ant drench. Pour in a steady stream about the width of a pencil. Try 4 gallons at first. If that does not do it, try a larger amount.

I have had success in making fire ants leave by sprinkling horticultural corn meal around the mound.

http://www.dirtdoctor.com/view_question.php?id=1341

Have you been able to tell if you have made progress or is the cold weather keeping them at bay?