First, don't feed them. Feeding will just encourage the robbers. Second, IF you feed them don't use essential oils or honey as it will only atrract the robbers. Third, minimize the size of the entrance on the hives. All of them. The robbers can't work so fast if they have a traffic jam at both the victim's door and their own door. Fourth, you can build a robber screen. The robbers tend to go by smell, the residents tend to go by remembering how they got in and out.http://www.bushfarms.com/images/RobberScreenHiveSide.JPGhttp://www.bushfarms.com/images/RobberScreenOutside.JPG
Another solution is to put some vicks vapo rub around the entrace to confuse the smells.