I had this problem for years. Grubs are not the problem either. Moles do eat grubs, but the main menu is earth worms. I always thought it was grubs and I applied grub killer for a few years with no effect over the moles. Then I tried traps, and sometimes they work, but there were too many moles and if I kill one, another moves in. So I contacted the chemlawn people and they came out and sprayed a special guaranteed to get rid of moles product. After an application, nothing happened. So they came out again, this time I had twice as many as before! They came out 5 times and the mole problem got worse each time. Then I got lawn beepers. Now I finally have no moles! I got my lawn beepers at Lowe's. For the sake of this being a family site, I will just say they look like a big flashlight:wink:. They use a couple D cell batteries. You take a 2x2 wood stake and drive a hole in the ground. then you push the beeper into the hole flush with the ground. You can mow right over it, no problem. Every 60 seconds or so, it emits a small beep and a small vibration..haha:wink:. The beep draws the moles in at first because they are curious. After about a week, the curiousity becomes utter annoyance. The constant beeping under ground drives them nuts, and the tiny vibration starves the moles away because they use vibrations to find food. A mole can hear/feel an earthworm moving through the ground! The moles completely evacuated my yard. The beeper covers a 50' radious. If you have a huge yard, you build a perimiter and they won't move into the center of your yard because they won't breach the perimeter. I think these things cost me $20 a piece. I used them for 1 yr and have not had a mole in the last 3 yrs..so the last two years, I did not even replace the batteries..heck I can't remember where the beepers are at now anyhow, but the moles are gone. Once in awhile I'll find a little mole path way out in the back 40, but I don't worry about way back there, just near the house and main yard area.
