Once a hive is being robbed it is almost impossible to stop. Far better to prevent it happening in the first place.
How do I know if my hive is being robbed?
A lot more bees around the hive than normal, not only around the entrance but crowding under the hive and around the cracks between the supers. Bees may be fighting at the entrance. In bad robbing situations the bees will rip open the comb and honey will pour out creating an even bigger problem.
Why do bees rob?
Robbing normally occurs in autumn after you have taken your honey off, There will be little or no nectar available so bees will risk trying to enter another hive to get the honey. Once one bee gets in and out safely he will head back to his hive to spread the news, soon you will have large numbers of bees wanting their share.
How do I prevent robbing?
Reduce your entrance right down to 10-20mm wide so the guard bees can defend the hive satisfactorily.
Take care not to spill honey or sugar syrup near the hive.
Only open the hive in the evening when not so many bees are flying
Fit a robbing screen to the front of the hive (more on this later)
What can I do if robbing has started?
Close the hive down for a few days.
Rub Vicks vapo-rub around the entrance to disguise the smell of honey
Cover it with a wet sheet to hide the hive from robbers, the home bees will still find their way in.
I have personally not had much success with any way to stop robbing!
How do I make a robbing screen?
You can purchase door screen mesh from Bunnings and fit it across the entrance with a timber frame allowing a small opening higher up above the entrance. The robber bees will try and head straight in, not realizing the entrance is higher up. The resident bees will soon find their way out and in.