Robbing

Robbing is when honey bees force their way into another colony's hive and carry off its honey; it is seen most often when the nectar flow stops. It develops quickly, can finish off a weak colony within a few hours and is one of the fastest routes by which diseases spread through an apiary. Most robbing starts with a beekeeper's mistake and can be prevented with simple measures.

What is robbing, and why does it happen?

When foragers cannot find nectar, they turn to the easiest source of sugar nearby. An unprotected hive, a comb left out in the open or spilled syrup is a far richer source than flowers. Once bees have found honey, they return to their hive and recruit others to the source, and within a short time hundreds of bees are heading for the same target.

That is why robbing starts when forage dries up. During a strong nectar flow bees don't rob; collecting from flowers is easier. Nor are honey bees the only robbers: in late summer, wasps and hornets also attack weak colonies and carry off honey and brood.

When does robbing happen?

• After the main flow: The midsummer gap after the main honey flow has ended is the riskiest period.
• Autumn: Natural forage dwindles and colonies are after winter stores.
• Drought: Nectar secretion stops during long dry spells.
• During and after the harvest: While supers are being taken off and during extraction, the smell of honey spreads through the apiary.
• Early spring: Colonies that came through winter weak or queenless are easy targets for their strong neighbours.

How do you recognise robbing?

• Fighting in front of the hive: Bees grappling with each other and falling to the ground, and dead bees in front of the entrance.
• Zigzagging, nervous flight: Robbers fly back and forth in front of the hive, swaying from side to side and scanning the surface for a way in.
• Attempts to get in through cracks: Bees prowling around gaps in the roof, joints between boxes and handholds.
• Wax fragments: Ragged capping debris from opened honey cells in front of the entrance and on the floor.
• Heavy departures: Robbers go into the hive light and come out heavy with full abdomens; they often climb up the hive front before taking off.
• Shiny, hairless bees: Individuals that have lost their hair in fights and look black and shiny.
• Abnormal sound and timing: A tense, intense roar; traffic that carries on into the evening when the other colonies have settled down.

Don't confuse busy flight with robbing

On a sunny afternoon, young bees' orientation flights also create a crowd in front of the hive. The difference is this: in orientation flights the bees face the hive and fly calm loops, there is no fighting, and it is over in fifteen to twenty minutes. In robbing there is fighting, dead bees and wax debris, and the picture keeps getting bigger.

Silent robbing is harder to spot: a strong colony carries off the honey of a weak or queenless neighbour without fighting. If a colony's stores are dropping fast for no obvious reason, suspect silent robbing. To find out which colony is doing the robbing, dust the bees at the entrance of the robbed hive with flour and watch which hive the white bees go into.

How does the beekeeper trigger robbing?

Most robbing results from beekeeper error:

• Leaving a hive open for a long time during a dearth, doing long inspections in the middle of the day.
• Leaving combs, supers, cappings or extraction containers out in the apiary.
• Open feeding or spilling syrup between hives.
• Leaving a wide entrance on a weak colony.
• Using cracked, worn hives whose boxes don't sit properly.
• Leaving the hive of a dead colony open.

How can robbing be prevented?

• Reduce the entrance: In a dearth, on weak colonies, to a gap just wide enough for one or two bees. On strong colonies too, set the entrance according to colony strength.
• Work quickly: In a dearth keep inspections short, work early in the morning or late in the afternoon, and cover frames you have taken out.
• Don't leave comb exposed: Keep supers and combs in lidded boxes, in a bee-proof store.
• Feed inside the hive: Give syrup or fondant with an in-hive feeder, in the late afternoon and to all colonies at the same time; wash away spilled syrup immediately.
• Seal cracks: A worn hive is a second entrance.
• Balance colony strength: Don't leave very weak colonies in the same apiary; unite the weak ones.
• Have extracted supers cleaned inside the hive: In the late afternoon, put them on strong colonies above a crown board; don't leave them out in the apiary.

What should you do once robbing has started?

1. Stop work in the apiary immediately. Don't open any other hives, and close up everything that is open.
2. Reduce the entrance of the hive being robbed. Leave a gap for a single bee. Closing the entrance completely can only be done for a short time and only if ventilation is provided; in hot weather a colony left without air will suffocate.
3. Drape a wet sheet or cloth over the hive. The cover hangs down over the entrance; the resident bees find their way, while the robbers' orientation is disrupted.
4. Make the entrance confusing. Placing an obstacle such as grass, branches or a pane of glass in front of it confuses the robbers. Anti-robbing entrance devices work on the same principle.
5. In severe cases, move the colony. If the robbed colony is taken a few kilometres away, the robbing stops. If you have found the robbing colony, dealing with it too (reducing its entrance) helps.
6. Check afterwards. The next day, check the robbed colony's queen and stores; unite or feed it if necessary.

Why should robbing be taken seriously?

Robbing is not just a loss of honey. Along with the honey, American foulbrood spores and varroa mites are carried from the robbed hive to the robbing colony. One of the common reasons for varroa numbers rising again quickly in autumn is mites brought in by robbing collapsing colonies.

That is why, when a collapsing or dead colony is found, the hive is not left open but closed at once, and its combs are not given to another colony until the cause has been established.