So do you plan to hunt this area again after this little "discovery"?

This is illegal activity, and if you don't report it, you've compromised your values as a sportsman. So I poach a big deer there out of seasonand you catch me. Do you report me? I have a rifle, you don't because you're out scouting. I WANT you to fear me.

In all likelihood, it's too late now. If this stuff was growing in tubs and that was the dirtbag you saw in the beater car, he's probably already moved his little "crop". Now someone else will be free to stumble upon him, maybe unwittingly and unarmed, when he IS armed.

Pass a violation of the law, you just set a new standard.