Reader Erica wonders why, if bees have evolved such an effective defense against microscpoic honey thieves, they couldn’t have evolved a more effective defense against larger ones like beekeepers. You know, Erica, I’m not entirely convinced that they aren’t working on that very thing right now. Since antiquity, honeys harvested from parts of northern Turkey have been notorious for their toxic effects. The reason, because they’re produced from the nectar either of of two species of rhododendron, R. luteum and R. ponticum which is known to contain compounds known as grayanotoxins.
These toxins aren’t poisonous to bees, however in humans they cause weakness, dizziness, flop sweat and vomiting. In some cases they can cause extreme low blood pressure, irregular heartbeat, shock and even death. Greek historian and mercenary Xenophon recorded, in about 400 B.C., the exploits of a Greek army traveling through what is now Turkey. It seems that some of the soldiers found and raided several hives along the way and were afflicted with vomiting and what has since been called “honey madness” or “mad honey disease.”
These sorts of stories make some people paranoid about rhododendron nectar here in the States, though there’s never been a recorded case of mad honey disease in this part of the world. That’s not to say that there aren’t other plants in the US whose nectar is potentially toxic to humans, however incidents of honey intoxication are extremely rare and almost never fatal. All of which means bees need to try a lot harder if they want to put us off their crop.