A serious problem in apiaries
Robbing can be a serious issue in apiaries, which can be caused by bees or wasps. I won't deal with robbing by wasps here, other than to say that wasps are much tougher than bees. They fly at lower temperatures and in a one-to-one situation a wasp will be the survivor. There are two main sorts of robbing by honey bees, "silent robbing" and what I am terming "normal robbing", which is what this page is about.
I will start by saying that in my opinion robbing occurs much more in managed colonies that it does in the wild. Wild colonies are usually strong, so are able to defend themselves and they select a home with an entrance small enough to defend, if not, they soon propolise it up to reduce it.
Many of the managed colonies I see that are robbed out are as a result of something the beekeeper has or hasn't done. A vulnerable colony can be robbed out very quickly, so "leaving it until tomorrow" or "I will sort it out when I get home from work" could well be too late.
Some signs of robbing.
Reducing the chances of robbing.
I have already indicated that robbing is usually the fault of the beekeeper, so prevention is far better than cure. Robbing is usually much more of a problem when there is a nectar dearth, especially when a nectar flow has ceased abruptly, which is more likely with a farmed crop such as oil seed rape than wild flowers.
During a heavy nectar flow I have often left honey, perhaps in a piece of brace comb, on somewhere like the roof of a hive for an hour or two and it hasn't been touched by bees, yet if the same thing is done during a nectar dearth it will be covered in bees in minutes. The point I make is that you need to assess the situation in order to reduce the start of robbing. You may be able to do something and get away with it, yet if done a week later will cause havoc.
Dealing with robbing.
Remember that if robbing occurs it is most likely to be the beekeepers fault, but if you have a problem you need to deal with it quickly.
Once a colony has started robbing it is unlikely to stop until it is satisfied that it has finished. Simply removing the source will divert the attention of the robbing colony elsewhere, which could be the least well defended colony. Whatever the source of robbing, whether it is a colony, a feeder or a pile of supers you will need to remove it quickly, but replace it with a small amount of honey or syrup. A spoonful or two on a plate or saucer will be enough. When the robbing bees have cleared it up they will calm down.
If robbing has only just started and the colony being robbed is strong in bees and queenright, then close the entrances of all colonies up to one bee space. You can put some small branches with leaves on in front of the hive to confuse the robbers. There is a reasonable chance that things will settle down, but keep a close eye on the situation, in case another colony gets picked on.
A method that is advocated in old books is to lean a sheet of glass (or polycarbonate) against the entrance. The rightful entrants will find a way round it, but the robbers will keep flying into the glass and give up. I have never used this method as I have never had to, so I don't know if it works or not.
If there is only one colony doing the robbing and one being robbed it is often sorted out by swapping places. This seems to confuse them and generally works.
If the robbed colony has taken a bit of a beating, then close it up and move it 3 miles or more away. In it's place put a brood box with some honey on a plate or saucer inside, or if there is a frame in another colony, preferably the robbers colony, with a small amount of liquid stores in, then place that in it. Once the robbers have cleared it up they should quieten down and return to normal.