Do you know what drives bees bananas?
Well not the banana itself, but the smell of bananas. Just a whiff is enough to make bees go ballistic. Bananas should really carry a health warning:
Bananas can cause bee attacks – do not picnic on bananas unless wearing protective clothing
You'll never catch beekeepers eating bananas because they know that the chemical that gives bananas that distinctive smell is the same chemical that bees use as a sting alarm pheromone. It's called isoamyl acetate, or more commonly, banana oil.
Isoamyl acetate is widely used as a flavouring, from pear drops to banana-flavoured yoghurt, and it's even used in some varnishes and lacquers. It smells nice – just like bananas!
But the bees hate it because the smell of isoamyl acetate means there's trouble, which means they're going to sting someone and then they're going to die.
It all starts with the guard bees which spend their time patrolling the hive entrance keeping out intruders. Usually there are four or five guards though if the colony is being harassed, by wasps for example, the guard may increase to 20 bees. That normally suffices but every now and then the guards can't cope with an intruder, so they call for reinforcements.
They do this by extending their stinger and releasing isoamyl acetate from a gland at its base. To make sure the odour of banana rapidly diffuses through the hive the guards fan their wings at the same time. The response can be spectacular; dozens of soldier bees rush out of the hive looking for a fight.
That's usually the moment when you see a beekeeper frantically puffing away with their smoker in an attempt to try and mask the smell of bananas and calm the bees down – but it doesn't help. What they should try instead is aromatherapy.
For those unfamiliar with quack medicine aromatherapy 'offers some of the best remedies for easing stress by using natural oils to enhance psychological and physical well-being'.
Probably tosh, but it seems that when it comes to bees there is scientific evidence showing that certain flower oils really do make bees less aggressive. A recent study found linalool (found in lavender oil) and 2-phenylethanol (found in rose oil) significantly reduced aggression in honey bees enraged by the sting alarm pheromone, and the effect was not simply due to the pong of flowers masking the scent of bananas.
Instead, what seems to be happening is that the soldier bees get two scent messages; the one from the banana oil says 'Go out and die for your colony!' but the one from the lavender oil says ...
And given the choice between certain death and the promise of a little snack, soldier bees choose the snack.
Most beekeepers wont be surprised by this; during a strong nectar flow the hives are fragrant with the smell of flowers and bees are very calm.
I'm going to try aromatherapy instead of using my smelly old smoker. Lavender flowers (fresh or dried) infused in hot water, then allowed to cool and filtered into a plant sprayer. A few sprays at the hive entrance and a few more when the roof is off should suffice.
But just in case it doesn't work, I'll put a dab or two of 2-phenylethonol behind my ears to ensure that what ever happens, I still come out of the experiment smelling of roses!
1. “Appetitive floral odours prevent aggression in honey bees” Nouvian et al. Nature Communications 6, 10247 (Dec. 2015)