I now believe that you need to be direct with trainers about what you expect at your facility if they are going to work there. As the barn owner, everything that happens at your barn is a reflection of your business and that includes what trainers do. How they run their business will affect your business in either a positive way or negative way.
If a trainer is not doing their job or doing things that you don't approve of than it becomes your business as the barn owner. I have had a few times early on in our business where I needed to talk to a trainer about the practices they were doing at the barn with the horses and even a couple of times when I knew they were being dishonest. The truth is in most cases the trainer will probably leave if it gets to the point where you need to talk with them.
I have found that if you refuse to except dishonesty from your trainers than you will attract trainers that have the same standards as you. They will want to work at a barn that is run with integrity and honesty and when you find a trainer like that, don't let them go. They will be a huge asset to your barn.
Thank you for the question!