I was distracted from my devotions to Our Microbial Overlords over the weekend by articles posted all over the place claiming the definitive cause of bee colony collapse disorder (CCD) has been confirmed. This is the phenomenon where entire colonies (or hives) suddenly disappear or die for reasons we don’t understand. Given about 30% of our food supply is dependent on pollination by the domesticated European honey bee (Apis mellifera) CCD is a bit of a pisser, frankly. Anyway, the paper confirmed the culprits behind CCD are the neonicotinoid pesticides banned in Europe last December for two years – a moratorium criticised by many, not least the manufacturers.
Despite their not being microorganisms I’ve always had a soft spot for bees – I can’t think of another organism that produces both sweetness (honey) and light (wax) and there are plenty of myths about bees that probably deserve a series of posts in and of themselves. Not by me, obviously; I’ll stick to the bugs but I make an exception here as there is a microbial element to the story.
Let’s look at the paper in question and a few other bee myths…
Neonicotinoids (neonics) are pesticides based on nicotine – which has itself been used as a pesticide since the 1700s. They are systemic insecticides – that means they are taken up by the plant and sit in the plant tissues until some biting pest decides to have a meal – and it then gets zapped by the pesticide lurking inside the plant. (There are other really cool genetic ways you can do this but let’s stick to the point for once).
This is good because it means the pesticide is tightly controlled in terms of its delivery. It means farmers need to spray less pesticide less often – also good – and this specificity and parsimony saves the farmers’ cash and reduces collateral damage from pesticides being slathered all over the shop.
But it’s also bad because this means the pesticide also ends up in nectar and pollen – precisely what bees take back to the hive.
Neonics In A Twist
So, the recent coverage concerns a paper out of Harvard claiming a slam-dunk correlation between colony collapse and neonic use. To be honest it starts going downhill in the first sentence which informs us colony collapse disorder (CCD) “appeared in 2005 / 2006”. This is Utter, Utter Bollocks (µ²B) as CCD has been around under a number of names for well over a century.
But let’s not let that basic and fatal flaw in the first sentence undermine the premise of this paper that neonics are indeed the bêtes noires and True Cause of colony collapse – despite CCD predating the first neonics’ use by 125 years.
To summarise they treated twelve hives with neonics, had six further control hives, no blinding and no apparent randomisation. Another big flaw is eighteen is a very small number – certainly far too small to draw too many conclusions from. Anyway, six of the twelve treated hives were abandoned versus only one of the controls. But let’s ignore the statistically insignificant sample size and the other flaws so far. Another key flaw is that hive abandonment is not always due to CCD. But again, let’s not let another basic error in the paper’s reasoning trouble us. Let’s crack on.
This paper’s claim that their data are proof that neonics are the cause of colony collapse is a conclusion I find challenging for a number of more important reasons. For a start CCD is complex. It’s far from completely understood. It’s most likely due to a bunch of different factors that militate against healthy, happy bee colonies all acting in concert: well-established stuff like infestation with Varroa mites, infection with a fungus called Nosema, other pathogens, pesticides, nutrition, stress – in short there’s a myriad of reasons bees can choose to abandon a hive. In this small study they have some degree of control for Varroa and Nosema but not for all the other factors. I’ve listed a few but there are many more bee ecologists and apiarists will be aware of that are beyond the ken of a simple microbiologist like me.
But even if we ignore the above, it’s the dosing régime of the neonics I find most suspicious. They put two different neonics – Clothianidin and Imidacloprid – into a syrup solution and fed it to the bees. The concentration of the pesticide in the syrup works out at 135 parts per billion. Which sounds pretty tiny. Which it is. They describe this is a ‘sub-lethal’ dose. Which apparently it is. I’m not arguing with 135ppb being a sub-lethal dose. (I find the dose calculations and methodology really obscure but I’m not an entomologist. I’m sure it makes sense on their planet).
What they don’t address is that bees ingesting neonics by feeding on plant tissue containing them encounter something more like 3ppb and certainly no more than 5ppb. Apparently bees are reasonably tolerant of neonics and can metabolise small concentrations like this with no apparent ill effect. But 135ppb?
Let me illustrate this with a human analogy. We are reasonably tolerant of ethyl alcohol. The liver converts it to acetaldehyde and even those of us who don’t imbibe still produce about a teaspoon a day merely through fermentation in our gut contents.
Anyway, have a pint of beer and it will most likely not impair your ability to drive too much. Have ten pints and it most likely will. This is still a sub lethal dose but it will have an effect. Drink 25 pints and if you can focus on the vehicle – let alone drive it – I would be surprised. If that level of beer leaves you unimpaired rather than rough as a badger’s arse I raise a glass to you.
So, bees are being fed neonics at a dose of 25-45 times that which they encounter in ‘real-life’ concentrations. Nicotine is a powerful alkaloid drug and nicotinoid pesticides share its neuroactive properties. Even though 25-45x the level of natural exposure might not kill bees I’m having trouble with the design of this experiment in terms of dosage alone. Add all the other variables they don’t control for and, well…
Other factors confound this analysis too; while driving through the canola prairies of Ontario a few weeks back I didn’t realise the 300,000 colonies harvesting open-pollinated canola have been largely unaffected by neonics despite their prolific use as a pesticide there – this is also the case in other regions that use neonics intensively such as the US Midwest. Despite a higher over-wintering loss in Canada this year the population seems robust (but winter did finish late this year – the snows in Ontario were still there until the back end of April).
So are neonics in the clear? Almost certainly not. Do they contribute to CCD? Expert opinion seems to think so. But like so much of biology it’s complicated. The cause of CCD is likely to be multifactorial. It will be interesting to see if any robust data come from the EU precautionary ban; if neonics are accelerating CCD this should give us a good steer.
But for now (and as usual) the media report the sound bite (“Harvard study shows neonicotionoids are devastating colonies by triggering colony collapse disorder“) and don’t take the trouble to analyse the paper. Or read it, apparently.
Bee Myths 101
While we’re here let’s look at some other bee ‘facts’. For a start anyone who tells you that aerodynamically speaking the bumble bee can’t fly knows the square root of bugger all about unsteady viscous fluid dynamics. The other canard that ‘no-one told the bumble bee it couldn’t fly so it just carried on doing so’ is also Utter, Utter Bollocks (µ²B) – by that logic if you didn’t know you were supposed to meet a squelchy, messy end when jumping from a cliff, you wouldn’t.
The Warriors of Woo have described bee pollen as a ‘perfect food’ that ‘contains all essential amino acids, vitamins and minerals’. For a start there is no such thing as ‘bee pollen’, bees collect pollen from flowering plants; pollen is a protein source, nectar provides sugar.
Did you know ‘honeybee pollen contains over 5,000 enzymes and co-enzymes, many times more than any other food’ ? This is also Utter, Utter Bollocks (µ²B): pollen does not contain ‘all known enzymes’ by a very long chalk. The only enzymes one might find in pollen regulate the metabolic functions of their respective plant species – because pollen comes from plants, innit. And if you eat plant enzymes they get digested down to their constituent amino acids, not absorbed intact because enzymes are bleedin’ proteins. So even if pollen enzymes were of any utility to us (which they ain’t) they’d still get digested before they could have any conceivable effect.
But Royal Jelly – basically worker bee spit – really is incredibly nutritious. No, really – it is. For bee larvae. That hasn’t stopped it being imbued with mythical qualities – boosts your immune system, fights ageing and lowers cholesterol – but those claims are just that. Myths. But I suspect the EFSA report on this and some other supplements will just fuel confirmation bias for the True Believers.
Propolis is basically ‘bee glue’ that they use as a structural material in hives. Bees process sap and other resins – including tar, mastic and caulking we use in buildings that they inadvertently collect – for similar purposes. Propolis has been shown to have some interesting biological activity – which is unsurprising as it’s packed with flavonoids as well as other stuff. In vitro flavonoids exhibit cell-killing properties that may find clinical utility one day (hint: ‘clinical’ tends to mean proven in clinical trials rather than some Utter, Utter Bollocks (µ²B) on the Internet).
But in vivo propolis is also a cause of an increasing number of cases of allergic contact dermatitis. And renal failure. A key issue is that propolis is not a single substance and its composition varies depending on where you harvest it, because bees will process resin and sap from local plant varieties. Just because it’s ‘natural’ and contains some biologically-active molecules doesn’t make it necessarily good for you. Dog turds are natural too but you won’t find me using them as a dietary supplement or skincare product.
Honey – while I’m not a fan of it myself – does have some cool properties. It can be used on wounds and burns because its sugar content makes it osmotically very challenging for Our Microbial Overlords. But it is true that untreated honey is a Bad Thing for babies as it’s a reservoir for Clostridium botulinum spores. Ditto using raw honey in wounds – C. botulinum spores are the last thing you’d want in a deep, anoxic space anywhere about you; botulism is never a good look – even when the incredibly potent neurotoxin it produces is sold as Botox®.
There are plenty of other Bee Woo combinations out there – bee venom acupuncture or mesotherapy, anyone? – but those are for another day…