Trespassing?

There have been 3 ladder stands put on the private property that I have permission to hunt. I wrapped the ladder with some duct tape and wrote on it with a sharpy. "private property - do not hunt - remove stands - others have permission"

I really don't want to bother the owner who gave me permission to hunt the land, however he did tell me I should be the only one there.

Is there a better or legal way to remove the trespassers?

Tim