It hasn’t just been 2020 for humans. My apiary has had lots of robbing problems this year. From what I’ve learnt, robbing occurs mostly during summer. The main reason for it is a lack of nectar sources in the vicinity of the hive and a large crowd of older forager bees. The problem should disappear as the weather grows colder and as these older bees die, but! I seem to have a breed of super-monster bees in some of my hives; The last robbing casualty fell around the end of November!
Some beekeepers believe that robbing isn’t really a problem. They believe the phenomenon will show which hives are strongest and therefore have the best genetics. There might be some truth to this, but in modern day practical settings, robbing also has negative effects on the ‘winning’ hive. Effects so severe that they may end up killing even the strongest hives.
Honey comb and bees in good condition 
Aftermath of robbing, no bees left and comb destroyed
Problem 1: Varroa
Robbing means honeybees enter a hive that isn’t theirs to rob the honey inside, bringing it back to their own hive. While moving around in the ‘victim’ hive, these bees will pick up varroa mites that are present and bring those back to their own hive. If for some reason it hasn’t been possible to treat all your hives at the same time, or your treatments aren’t synchronized with those of beekeepers nearby, robbing means treated hives pick up mites from untreated hives.
dead bee with varroa 
Varroa destructor
Problem 2: Disease transfer
Perhaps you are lucky. You don’t have hives that show signs of disease. You might be a beekeeper with a consistent method of replacing out old comb and treating your own hives. If this is the case, disease transfer is probably less of a concern for you. But you cannot know what the situation is like inside hives that belong to other beekeepers nearby. These other beekeepers could be nomadic beekeepers and you might not know they’re around. Their bees might come to rob yours, or vice versa, and disease will be introduced. Robbing causes the victim to be significantly weakened and therefore more susceptible to this disease.
Problem 3: Depletion of stores and bees
This one is obvious. If a hive is ‘successfully’ robbed, most or all of its honey will be removed and much of the comb destroyed to the point where the bees will not be able to repair it. Brood will be killed, especially when wasps find the weakened hive after it’s already been robbed. The queen might be killed and many bees will perish in fights. A hive might be reduced to such a small number of bees that it cannot save itself any longer. In this case joining the weakened hive with a stronger one, may be the only way to help these bees.
Comb destroyed by robbing 
Bottom tray on a severe casualty hive
So far, the hives that suffered severe attacks died during the summer, close to when they were robbed. Some I managed to combine with other hives (and treat for varroa!) before the remaining bees inside perished. Now, halfway December, I’ve already lost at least one ‘strong’ hive, one that I had to prevent from robbing other hives. I hope we don’t suffer any more casualties, but apart from sublimating more oxalic acid there really is nothing I can do.
Next year, our new garden should be filled a little more with the nectar-providing flowers we’ve sown and planted. This should help bridge the times when naturally occurring nectar sources aren’t plentiful enough.
The Lowland Homestead 