Well, if you notify the warden I dont know that you are going to be in trouble with the neighbors. Do you live somewhere that the warden could haphazardly be driving down the road and see a huge mound of corn?
Notify the warden about it, tell him you would appreciate it if he would approach it as
"Hey guys how ya doin today? I was driving down the road here on my way to ...whatever... and couldn't help but notice you spilled all this here corn. You plan on cleaning it up soon?"
Now they know that he knows, and they'd be complete fools to continue. Plus now the neighbor boys are on his radar. Or, if the warden wants to just cut to the chase and write them up for the offense, that's his decision. All you have to do is notify, it's not up to you to decide if you want to "press charges" in a situation like this.