The truth about pesticides and bees?

Each week Riverford Organic delivers a vegetable box to our door. Nestling among the mosaic of vegetables is a newsletter from the Riverford boss, Guy Watson.  This summer he has moaned, justifiably, about the state of the weather and the effect on his farming business. A week or so ago, the litany of moans was interrupted when he used his newsletter to publicise a new Soil Association campaign, “Keep Britain Buzzing”. The campaign calls for a ban on a group of insecticides named neonicotinoids. The neonicotinoids are widely used to kill insect pests on crops such as Oil Seed Rape but there is increasing concern that they may also be harming bees.

I hadn’t really woken up to the problems that bees were facing until earlier this year when there was a flurry of letters in the Guardian under the headline “The truth about pesticides and bees”. The palpable anger of the beekeepers, expressed in this correspondence, was tinged with despair that their bees might be harmed by these insecticides and nobody cared.

Beehives in Devon                                                         Beehives in Devon


The letters were responding to an article that had described the findings of two papers published in the high profile journal Science on the effects of neonicotinoid insecticides on bees.  The two new papers looked at the effects of these insecticides under “field conditions” using “field-realistic” amounts of neonicotinoid and the results were striking. One paper, from the University of Stirling, reported an 85% reduction in queen production by bumblebees that had consumed neonicotinoids. The other paper, from INRA in France, reported that neonicotinoids reduced the ability of honeybee workers to find their way back to their hives. Both studies showed effects on bee behaviour that could threaten survival of the bee colony without directly killing the bees.

These two papers have had a huge effect on policy but to consider this properly, I need to fill in a bit of background about bees and about these insecticides.

The neonicotinoids were introduced as insecticides in the 1990’s and had the advantage that they were less toxic to mammals than the chemicals used before. They work by acting as insect neurotoxins but they are also toxic to other organisms including earthworms and butterflies. Unlike other insecticides the neonicotinoids act systemically. They are typically applied as soil or seed treatments and given their water solubility, they distribute throughout the growing plant.  This means that insects coming to feed from the treated plant will be exposed to the insecticide. Among these insects, there may be bees gathering nectar or pollen. Imidacloprid, a popular neonicotinoid, is one of the most widely used insecticides in the world, making millions for the agrochemical company Bayer.

Bees (honeybees, bumblebees and solitary bees) play a very important role as pollinators and make a major economic contribution to agriculture. They pollinate up to three quarters of our most vital crops and favourite foods and it has been estimated that without bees it would cost UK farmers £1.8 billion each year to pollinate crops.  Bees are also essential pollinators for our gardens, parks and countryside. Without bees, not only would food be much more expensive but our countryside would look entirely different.

There is no doubt that the neonicotinoids can kill bees if not used correctly. There have been several instances of large scale bee deaths following inappropriate or careless use of the chemicals and some countries have introduced partial bans. The key question has been whether the neonicotinoids are harming bees when used as directed by the agrochemical companies who make them. The agrochemical companies say they are safe. Many others, however, fear that there may be unintended effects of the neonicotinoids on bee populations; they are, after all, insecticides and are designed to kill insects.  Protocols for testing for unintended effects on bees were developed for insecticides used in single spray application. Although these protocols were used to evaluate the neonicotinoids, they are inappropriate for systemic insecticides that will be present for prolonged periods and they focus only on honeybees. They also fail to assess fully the more subtle effects of insecticides on bee society. Honeybee and bumblebee colonies depend on complex behaviours and there had been a growing concern that neonicotinoids might exert sub-lethal effects on these activities.

honeybee on lavender 3                                                         Honeybees on lavender

This was where the two new papers made their impact. They provided important new evidence under field conditions that the neonicotinoids did indeed have sub-lethal effects on bee behaviour that could threaten survival of the colony.  As a result they were widely reported in the media and had a huge effect. The French study on honeybees used the neonicotinoid, thiamethoxam and by June the French government had banned this compound. The UK response was more phlegmatic. DEFRA were asked to comment and eventually did so concluding that “recent studies do not justify changing existing regulations”.  Some sections of the press have been very critical of DEFRA’s reply including Damian Carrington of the Guardian and Michael McCarthy of the Independent. By September, the Environmental Audit Committee of the House of Commons had decided to set up an enquiry in to these insecticides and DEFRA’s recent response.  That Committee is currently holding hearings on the topic, having received written submissions from interested parties. If you have the time you can watch the proceedings on Parliament TV.

Buff-tailed Bumblebee on Bergamot                                                  Bumblebee on bergamot

In the meantime the science has moved on. Another field-realistic study on bumblebees appeared in October, this time from Royal Holloway College, showing that this species of bee is vulnerable to mixtures of pesticides. Bumblebees exposed to combinations of insecticides (neonicotinoid and pyrethroid) exhibited impaired foraging and increased worker mortality. A lab-based study from the University of Exeter was also published and compared the effects of neonicotinoids on bumblebees and honeybees. Bumblebees were very sensitive to the neonicotinoids which reduced their feeding rate.  Honeybees were unaffected in this test system.  A clear case for the vulnerability of bumblebees to the neonicotinoids is emerging and given the importance of bumblebees as pollinators this ought to be taken seriously. Perhaps bumblebees are more sensitive to neonicotinoids than honeybees, making the case for safety re-evaluation more urgent.

Further potentially significant evidence has been uncovered recently by the Environmental Audit Committee about the persistence of one neonicotinoid in soil. Imidacloprid had been thought to degrade relatively quickly but new evidence suggests it may persist in soil so that with repeated annual applications a build up of the chemical could occur. This could be detrimental to insects that overwinter in soil.

The battle lines are now clear. On one side we have the Soil Association, also Friends of the Earth, Buglife and journalists from the Guardian and the Independent. On the other side there are the agrochemical companies, Bayer and Syngenta and the National Farmers Union (NFU). The battle is currently being waged at the Environmental Audit Committee but I would imagine there is furious lobbying going on behind the scenes. In a separate and surprising development the Environment Secretary, Owen Paterson has asked for new advice on the practical consequences of banning the neonicotinoids. It’s currently difficult to predict the outcome of this battle.


The more I read about this topic, however, the more I wonder how we got to this point? These chemicals are being ladled on to crops (and also gardens, golf courses and school playing fields) in huge amounts each year with little regard to outcome apart from ensuring the profitability of intensive farming and of agrochemical companies. The key players betray their attitudes to the situation by their public utterances. For example, when France banned thiamethoxam, Syngenta commented: “This is a dark day for French and European agriculture” adding that 30% of the Oil Seed Rape in France would now be lost. In their written submission to the ongoing parliamentary enquiry the NFU say “If neonicotinoid insecticides were not available, farmers and growers would use less effective insecticides that pose a greater risk to bees and other insects”.

It feels to me that we need to take a fresh look at the use of the neonicotinoids given the way the evidence is stacking up, focussing especially on their detrimental effects on bumblebees. In the past, insecticides were used on an “as needed” basis – if a crop had an insect problem then it was sprayed. Because the neonicotinoids act systemically, they can be used as a seed treatment and distribute throughout the plant. This is very convenient for the farmer, but it means that neonicotinoids are being used as insurance against potential pests rather than “as needed”. For example, almost all of the Oil Seed Rape now grown in the UK derives from seed treated with insecticide. If neonicotinoids persist in soil this becomes all the more damaging to the environment. We need to ask: “What would happen if we did not treat a crop with insecticide? Might we be better reverting to older insecticides that are used when required? Should we plant bee-friendly areas around fields?”


But, why should we worry about the bees? There are now so many other issues that should concern us. One reason is economics. Bees play an essential role as pollinators and it would be very expensive to arrange pollination otherwise, so we need to protect them. I believe there is another argument that is not so clearly defined. When I became interested in the plight of bees I visited several beekeepers so that I could learn more. I was able to look inside honeybee hives and spot the queen and got to know the stratification of the colony and the elaborate chemical and behavioural signalling that goes on. I also spent some time watching and photographing the bumblebees and solitary bees in our garden. This is all getting a bit “touchy feely” but it empathises for me the need to look after nature and to conserve species. Our apparent disregard for bees, our readiness to kill them, is an appalling indictment of our attitude to the natural world.

About Philip Strange

After more than 30 years as an experimental scientist, I decided to have a complete change and moved to the West Country. I now write about science for several magazines and web sites and blog at
This entry was posted in Insects, Science Policy and tagged , , , , , , , , , , , . Bookmark the permalink.

24 Responses to The truth about pesticides and bees?

  1. We have bumble bees in our wall due to an unfilled plank. They are no problem and are fun to watch. Even if we do have to evict a few here and there. I refuse to use insecticides for anything and have done for some years with only one application (and it didn’t work either I might add) of anything.

    viv in nz

  2. Thanks for this, Philip. I didn’t know anything about neonicotenoids before reading your post. Highly disturbing stuff – I wonder what the situation here in Canada is? Must investigate – especially since rapeseed/canola is a huge cash crop here.

    • Thanks for reading the post, Richard. I dont know much about the Canadian situation but I would be interested to hear. I imagine that the the rape seed/canola is being treated with neonicotinoids

      • Cath@VWXYNot? says:

        Nice article, Philip – interesting stuff. I wonder if these chemicals act synergistically with whatever causes colony collapse disorder, meaning that the bees face a double whammy?

        Richard, there have been a few attempts in Vancouver and BC as a province to ban pesticides for everything but agricultural use – i.e. banned for lawns, golf courses etc. But nothing has passed so far. Hopefully the widely predicted change of provincial government next year will help – it was the opposition who introduced the defeated bill. A municipal ban wouldn’t do much as it’s just too easy to drive for half an hour and buy the stuff somewhere else…

        • I’m surprised that Vancouver hasn’t passed something like this. We’ve had pesticide and herbicide bans here for a couple of years, at least for residential use. Golf courses are I believe exempt, being businesses. Of course, you can still buy the stuff in your local Home Depot – it’s locked in a cage marked “for noxious weeds / pests only”. So I guess you just have to tell them you’ve got Poison Ivy, or a plague of locusts, or something.

          • Is the ban in Ontario popular, Richard? I had intended to include it in the article as an example of good practice but when I looked around I sensed there was opposition – or have I just picked up the shouters on the internet?

          • I’m not certain that it’s super-unpopular… but I live in a remarkably apathetic suburb so it’s hard for me to tell.

        • Thanks Cath, I am pleased you liked the article.

          Its very difficult to pinpoint a cause of CCD as honeybees face many threats. In the US, where CCD has mostly been seen, bees are very stressed by migratory beekeeping and monoculture, plus they also have Varroa mites and viruses that come along with the mites. If you then add neonicotinoids as well, then perhaps they just cant cope.

  3. Emily says:

    Have you come across the barefoot bee keeper ( He gave a talk at Schumacher College last year as part of the Earth Talks they run – it was pretty interesting.

    • Thanks, Emily. Yes, I came across the barefoot beekeeper recently via his web site. The methods of Natural Beekeeping look interesting and I know beekeepers who use some but not all of the methods quite successfully. I discovered that he and the South Devon Friends of the Bees meet monthly at a pub, the Kingsbridge Inn, that is less than five minutes walk from our house, so intend to get in touch.

  4. cromercrox says:

    It’s a no-brainer. Indiscriminate use of systemic insecticides is going to harm bees. The problem is what to use instead. The world can’t suddeny go organic – we don’t have the land surface required. However, people who havr gardens and small plots can help by staying away from pesticides wherever possible. Here at the Maison des Girrafes we encourage frogs to eat slugs, use coffee grounds to deter slugs and snails, and rely on the general biodiversity to get rid of any troublesome insects. This does mean that our veg patch is occasionally devastated by caterpillars – which would be a problem if you depended on your crops for your livelihood.

    I think the answer would be to genetically engineer your crops to produce insecticide, such as Bt toxin, rather than treating the plants with systemic insecticide. This would kill insect pests but would have no effects on pollination.

    • Thanks Cromercrox. I agree it’s a no-brainer but some people are prepared to let the bees take the hit rather than lose a bit of cash themselves.

      We also use the Maison des Girrafes pest control system in our garden.

      There has been some concern about Bt toxin and bees but when I had a quick look at the scientific studies I could see no reports of adverse effects so your idea would probably work.

  5. Pingback: The tortuous tale of bees and insecticides | Philip Strange Science Writing

  6. Emily says:

    Defra launched a public consultation this week (10/01/13-09/03/13) on their proposals to help beekeepers protect from pests and diseases:

  7. Pingback: Bees in Devon | Philip Strange Science Writing

  8. Emily says:

    Thanks for the up-dates, the rspb retweeted the link below this morning about a march at Parliament Square on Friday in support of the UK giving backing to an EU ban:

  9. Emily says:

    Also I don’t know if you saw this review of the threats to pollinators from the Centre for Ecology and Hydrology published last week (22nd of April) (and in the press a bit):

    Adam J Vanbergen and the Insect Pollinators Initiative. 2013. Threats to an ecosystem service: pressures on pollinators. Front Ecol Environ 2013; doi:10.1890/120126.

    (not open access unfortunately)

  10. Emily says:

    Great thanks! There is a technical report from Greenpeace Research Laboratories (based at the University of Exeter) reviewing the factors that put pollinators and agriculture in Europe at risk out (and free) if you haven’t seen it:

  11. Pingback: The March of the Beekeepers | The Occam's Typewriter Irregulars

  12. I had no idea that Greenpeace had labs at the University of Exeter so thanks for alerting me to that and for alerting me to the report, which I will read.

Comments are closed.