A few years ago we were troubled with a yellow jacket nest in the ground. I tried spraying wasp and hornet spray into the hole in the ground, but it did no good. Then the thought came to try flooding the nest. Being too chicken to place the garden hose in the hole, I stood a safe distance away, and practiced gently throwing the hose toward the nest. I had to drag the hose back a number of times, but when I finally was able to get it next to the hole, I turned the water on low and just let it run steadily for two or three days. It did the job nicely. We have soil that drains readily, so there was no damage to nearby plants. I don't know how this would work with hard-packed clay soil.
Whatever method you use, I wish you success.
Kat
