Robbing Screens to Protect Honey and Prevent Mite Spread

We all love honey bees. They're models of cooperation, of coordinated effort, of industriousness, of self-sacrifice for the good of their family. But that's not all bees are: They're also dirty little honey thieves! 

All of that labor throughout the year, visiting flower after flower to collect tiny amounts of nectar to make their honey, makes our bees seem like model workers. The reality is that the bees visit those flowers because they're the only free source of sugar in the area. If you offer a forager the choice between sugar-rich honey or watery nectar, she'll choose the honey every time. That's why our nice bees will sometimes mount an attack to steal honey from weaker colonies nearby. 

These robber bees can gang up on a colony and rob them out in a matter of days. Other times, a small number of robbers will sneak into a colony, evading or defeating its guard bees, and then will collect their ill-gotten honey before they return home. The first kind of "overt robbing" is obvious to a human observer, and can completely devastate the robbed hive. 

The other kind of robbing is much more subtle. "Covert robbing" by honey bees can be hard to recognize unless you're looking for it. You may notice guard bees and robbers fighting at the entrance, but you may completely miss it. 

So what should a beekeeper do to protect their bees from these unscrupulous honey thieves? The answer is to use an entrance reducer or (even better) a robber screen. 

Entrance reducers will give your guard bees a smaller area to protect and can help them exclude occasional robbers. The problem with entrance reducers is that robbers and guards will still encounter each other at the smaller entrance, and a weak hive can still be overwhelmed by the robbers and lose all of its honey.

Robber screens are a far more sophisticated device because they take advantage of bee behavior to keep robbers out. Robber screens use a screen mesh or other small holes to let the smell of ripening honey drift out of the entrance to the hive. The robbers will be attracted to the odor, and approach the screen, trying to get in. Little do the robbers know that they've been tricked! The true entrance to the hive, used by the resident bees, is at the top of the robber screen where very little honey odors are escaping. The would-be robbers approach the screen, fail to get inside, and eventually move on, all while the resident bees continue their foraging. 

Entrance reducers and robber screens can be used to protect your bees and their honey from robbers. But there's another benefit to these anti-robbing devices that is often overlooked. In addition to robber screens keeping honey inside the potential victim hive, it also keeps agents of disease like varroa mites inside the hive! Robber bees can quickly collect mites from the weak hives they rob, and bring them back to their home colony. Preventing robbing in your apiary (or between neighboring apiaries) can keep parasites and pathogens where they are instead of spreading them through your apiary. Robbers can collect many things in addition to honey, like varroa, mite-transmitted viruses, bacteria (that cause diseases like American foulbrood and European foulbrood), and fungi (that cause diseases like nosemosis and chalkbrood). The worst part is, many colonies become weaker and weaker as they get sicker and sicker, so the sickest colonies are usually the ones most likely to fall victim to opportunistic robber bees!

So a robber screen protects your weaker colonies and saves their honey from being pilfered, but it also reduces disease transmission between colonies. If you've got parasites or pathogens in a hive, they'll stay in that hive and won't spread through the whole apiary. More importantly, if your neighbor has parasites and pathogens in their hives, a robber screen could help keep those diseases in his apiary and out of yours. Since robbers can fly as many as ten kilometers to find a victim, you might consider gifting all of the beekeepers in your neighborhood a robber screen for each of their hives. You can tell them it's to help their bees protect their honey, but we'll know the real reason is to keep your bees safe from disease.