I add jello or vanilla to my bait when the trapping gets serious. I dig a hole, put out the bait, cover with a piece of plywoood, and then set the trap on top of that. Once the hogs are in the trap, their weight keeps them from being able to root up the bait. Other hogs will smell the bait and try to enter.

I know some people that put diesel in the corn to keep other critters from messing with it. I didn't think my luck was as good with that as it was the other way, so I quit. But some around here swear by it.