A couple of weeks ago the Society of Chemical Industry held a meeting in London to discuss “Are neonicotinoids killing bees?” As you might guess from the name of the people organising it, this seems to have been a rather one-sided affair; a bunch of lobbyists from the agrochemical industry, and a hand-picked selection of scientists consisting overwhelmingly of those known to have pro-pesticide leanings and/or receive funding from the agrochemical industry. I was unable to attend this travesty of a meeting, but I did get a chance to hear how it was reported on BBC Radio 4’s Farming Today, and BBC gave me two minutes to give an off-the-cuff response to comments made by two attendees, Norman Carreck[1] (of Sussex University and the International Bee Research Institute) and Peter Campbell (of Syngenta). Here I give a slightly more detailed and considered response.

            Norman’s summary can be paraphrased as “It is all complicated and confusing, we can’t really be sure what harms bees. The moratorium on neonic use on flowering crops[2] is forcing farmers to use older, nastier chemicals that we know little about. This could be worse for bees than using neonics”. Peter stated categorically that in real world situations neonics don’t harm bees. He pointed to an authoritative Swedish study, the largest field trial yet performed to examine the effects of neonics on bees, which found no effect on honeybees of placing their colonies next to a treated oilseed rape crop for one year (Rundlof et al. 2015). Any politician listening to this would be inclined to think that the scientific evidence against neonics is far from clear, and that the current moratorium might be doing more harm than good. Of course this is exactly what the meeting was intended to achieve – job done. The pesticide industry makes billions of dollars every year from these chemicals, and spreading doubt and confusion is a great tactic to prevent policy makers from taking further action, and to encourage a post-EU UK government to abandon the moratorium altogether.

            Let’s look at what we actually do know with certainty about neonics:

1) These are very widely used neurotoxins, applied extensively to many arable, horticultural and ornamental crops, and also found in veterinary products such as flea treatments for dogs and cats. They have high persistence so last for years in soil (Goulson 2013; Bonmatin et al. 2015). They are water soluble and are now routinely found in streams and ponds around the world (Bonmatin et al. 2015). They are also found in the pollen and nectar of wildflowers growing near treated crops (Botias et al. 2015; David et al. 2016), as well as in the pollen and nectar of the crop itself.

2) When we place honeybee or bumblebee nests onto farmland, the pollen and nectar stores that they gather often contain a cocktail of several neonics (and a bunch of other pesticides, mainly fungicides). Concentrations of neonics in their food typically range from 1 to ~10 ppb, sometimes more (which of course means that your breakfast honey also likely contains these neurotoxins) (Botias et al. 2015).

3) If we dose honeybees or bumblebees in the lab or in cages with food spiked with these same concentrations of neonics (i.e. between 1 and 10ppb), we get the following range of effects: reduced longevity, impaired immune response, impaired learning, reduced egg laying in queens, reduced fertility in males (reviewed in Pisa et al. 2015; Straub et al 2016). [Note that not every single study finds the same effects and a few have found no effects, presumably due to differences in methods, the particular neonic and dose used, the age and health of the bees used, the bee species studied etc. It isn’t simple, but the overwhelming evidence is that neonics do harm bees at field-realistic doses]

4) When bumblebee colonies are exposed to field realistic doses (Whitehorn et al. 2012; Arce et al. 2016) or exposed to treated crops in a field setting (Goulson 2015; Rundlof et al. 2015), the colonies perform very poorly, grow slowly and produce few queens.

5) Solitary bees perform poorly when near treated crops; fewer wild bees are found on the crop itself, and Osmia bees fail to nest entirely near treated crops (Rundlof et al. 2015). 

6) Declines of wild bees and butterflies in the UK strongly correlate with geographic patterns of neonic use (Woodcock et al. 2016; Gilburn et al. 2015). [The pesticide industry immediately respond to this by saying “correlation is not proof of causation”. Of course this is also what the tobacco industry said about cancer and smoking. Correlation is not proof, but it is good confirmation of other evidence]    

7) When honeybee colonies are exposed to treated crops, the deleterious effects on individual bees described in (3) do not seem to translate into significant harm to the colonies, at least inside a single year (e.g. Pilling et al. 2013; Cutler & Scott-Dupree 2007; Rundlof et al. 2015). Note that all but one of these studies (Rundlof et al. 2015) were performed by the agrochemical industry themselves or funded by them, and thus should probably be treated with a pinch of salt. If we take them all at face value, this does not rule out the possibility that exposure to neonics might contribute to colony loss in the longer term, for example by reducing queen longevity/ fecundity, but it does seem that there is no dramatic and immediate effect on honeybee colonies in the way that there is with bumblebees and solitary bees. Perhaps the very large colonies of honeybees buffer them against the impacts of pesticides, at least in the short term.  

Overall, the case that neonics harm bumblebees is iron-clad. There are dozens of studies from lab to full field experiments that provide a convincing and coherent body of evidence. The case that neonics cause honeybee colonies to die has not been proven beyond doubt, though it would seem highly likely that having their food laced with neurotoxins at doses that are known to leave individual bees susceptible to disease, dazed and confused isn’t helping them cope with their many other problems.

To return to the comments of Peter and Norman. Peter was being deliberately disingenuous. In referring to the Swedish study (Rundlof et al. 2015) as demonstrating that neonics do not harm honeybees he was relying on the audience being ignorant of the fact that there are many other types of bee, and that this very study showed devastating effects on bumblebees and solitary bees which he thought better than to mention [in case you don’t know, bumblebees are enormously important pollinators of crops and wildflowers, as are some wild solitary bees – in the UK, honeybees contribute no more than ~30% of crop pollination, the rest coming from wild insects].

Norman’s “it is complicated and confusing” is a cop-out. Science is complicated, that is why it takes years to train as a scientist, but it is our job to make sense of the evidence and summarise it in a useful and clear way. It is pretty clear to anyone even a little familiar with the scientific literature on wild bee declines and honeybee colony losses that these phenomena are due to multiple causes, including loss of flower-rich habitat, spread of parasites and diseases, and exposure to pesticides (Goulson et al. 2015). If we want to address bee declines we need to tackle all of these issues, and we need to do so with urgency, not stand around arguing about which is worse or saying we need to do more research before we take any action. 

Norman’s point that the neonicotinoid ban has forced farmers to use older, nastier chemicals that we know little about is interesting, and is an argument I have heard trotted out many times by the agrochemical industry. The neonic ban led UK farmers to increase spraying with pyrethroids in September (on young oilseed rape crops). These are older chemicals, but to say that we know little about them is nonsense. They have been in use for decades and are very well studied. If they were sprayed onto a crop at the time of flowering they would kill lots of bees. However, spraying them in September onto seedling oilseed rape is likely to have minimal impacts on bees; most wild bees are gone by then, and honeybees have no reason to be visiting the crop. Pyrethroids have very low persistence compared to neonics, so they will be not hang around until the spring when the crop flowers. Norman knows this well, since he spent most of his career working at Rothamsted, the very place that developed pyrethroid insecticides. Of course it would be better still if farmers investigated non-chemical means of managing their crop pests whenever possible, adopting an Integrated Pest Management approach, but that is for another day.

Despite what the agrochemistry industry and their supporters say, the evidence linking neonics to bee declines is overwhelming. But industry will continue to say that black is white, that neonics don’t harm bees, just as some continue to deny climate change because it suits their financial interests. As the American author Upton Sinclair once said, “It is difficult to get a man to understand something when his salary depends on him not understanding it”. We urgently need to put pressure on our politicians to ensure that they ignore this rubbish and take proper steps to prevent the wholesale pollution of our countryside with persistent neurotoxins. More broadly, we need to find ways to reduce the grip of the chemical manufacturers on the way we grow food. Like Brexit or not, it provides a golden opportunity, freeing British farming from the Common Agricultural Policy, and making it possible to steer it away from industrial, chemical farming towards more sustainable methods. If we do not, we will lose bees and much else of our wildlife for ever.    

References (links provided wherever possible)

Arce, AN et al. 2016. Combining realism with control: impact of controlled neonicotinoid exposure on bumblebees in a realistic field setting. Journal of Applied Ecology, October 2016 DOI: 10.1111/1365-2664.12792

Bonmatin J-M., Giorio C., Girolami V., Goulson D., Kreutzweiser D., Krupke C., Liess M., Long E., Marzaro M., Mitchell E., Noome D., Simon-Delso N., Tapparo A. 2015. Environmental fate and exposure; neonicotinoids and fipronil. ENVIRONMENTAL SCIENCE & POLLUTION RESEARCH 22: 35-67.

Botías, C., David, A., Horwood, J., Abdul-Sada, A., Nicholls, E., Hill, E., Goulson, D. 2015. Neonicotinoid residues in wildflowers, a potential route of chronic exposure for bees. ENVIRONMENTAL SCIENCE & TECHNOLOGY 49: 12731-12740.

Cutler GC, Scott-Dupree C (2007) Exposure to clothianidin seed-treated canola has no long-term impact on honey bees. J Econ Entomol 100: 765–772

David, A., Botías, C., Abdul-Sada, A., Nicholls, E., Rotheray, E.L., Hill, E.M. & Goulson, D. 2016. Widespread contamination of wildflower and bee-collected pollen with complex mixtures of neonicotinoids and fungicides commonly applied to crops.ENVIRONMENT INTERNATIONAL 88: 169-178.

Goulson D. 2015. Neonicotinoids impact bumblebee colony fitness in the field; a reanalysis of the UK’s Food & Environment Research Agency 2012 experiment. PEERJ 3:e854.

Goulson, D. 2013. An overview of the environmental risks posed by neonicotinoid insecticides. JOURNAL OF APPLIED ECOLOGY 50: 977-987.

Goulson, D., Nicholls E., Botías C., & Rotheray, E.L. 2015. Combined stress from parasites, pesticides and lack of flowers drives bee declines. SCIENCE 347: 1435-+.  

Pilling et al. 2013; A Four-Year Field Program Investigating Long-Term Effects of Repeated Exposure of Honey Bee Colonies to Flowering Crops Treated with Thiamethoxam. PLOSOne http://dx.doi.org/10.1371/journal.pone.0077193

Pisa L., Amaral-Rogers V., Belzunces L.P., Bonmatin J-M., Downs C., Goulson D., Kreutzweiser D.P., Krupke C., Liess M., McField M., Morrissey C.A., Noome D.A., Settele J., Simon-Delso N., Stark J.D., Van der Sluijs J.P., Van Dyck H. and Wiemers M. 2015. Effects of neonicotinoids and fipronil on non-target invertebrates. ENVIRONMENTAL SCIENCE & POLLUTIONRESEARCH 22: 68-102.

Rundlof et al. 2015 Seed coating with a neonicotinoid insecticide negatively affects wild bees. Nature 521: 77-80

Straub, L. et al. Neonicotinoid insecticides can serve as inadvertent contraceptives. Proc. Roy. Soc. B doi : 10.1098/rspb.2016.0506

Whitehorn PR, O'Connor, S., Wackers, F. L. & Goulson, D. 2012. Neonicotinoid pesticide reduces bumble bee colony growth and queen production. Science, 336, 351-352

Woodcock, B.A. et al. 2016. Impacts of neonicotinoid use on long-term population changes in wild bees in England. Nature Communications 7, 12459.