David's blog posts tagged with 'bumblebee'

Bumblebees on Springwatch



Ah, the perils of live TV. They say never work with animals or children, so I fear I am in trouble. Tomorrow I am appearing live on "Springwatch in the Afternoon", broadcast from deepest, darkest Wales (an RSPB reserve somewhere near Aberystwyth). I'll be ineptly trying to plug my new book, A Sting in the Tale, while catching and handling bumblebees, talking about bumblebees, building a nest site for bumblebees, and being rude about garden centre bedding plants (which are rubbish for bees - intensive breeding has left them without nectar or pollen, or so bizarrely deformed that insects can't fit into them any more). What could possibly go wrong? 3pm, tuesday 4th April. Enjoy :)

Dave Goulson's research lab website

Neonicotinoids and bees; what is the fuss all about?



When I was first asked to support a ban on neonicotinoid insecticides, I was very sceptical. I’d previously been asked to sign up for campaigns claiming that bee declines were due to mobile phones, GM crops, overhead power lines, and various other eccentric or implausible notions. However, a review of the science suggested that there was something worth investigating, and for the last two years I seem to have had time for little else.

The issue has focussed largely on harm these chemicals might be doing to bees, both domestic honeybees and wild pollinators such as bumblebees. I’ll focus on bumblebees here, for they are the subject of my particular expertise. Neonics are widely applied as a seed dressing to crops such as oilseed rape, and being systemic they spread through the plant tissues into the nectar and pollen. They are highly toxic to insects; for example the “LD50” (the dose that kills half of test subjects) in honeybees is about 4 billionths of a gram. To put that in context, 1 gram – little more than the weight of a sachet of salt – would provide an LD50 to 250 million honeybees, or roughly 50 metric tonnes of bee. They are neurotoxins, binding to neural receptors in the brain and causing swift paralysis and death.

Until recently, there had been few studies of neonics and bumblebees, all small scale and nearly all performed in cages or glasshouses. Taken together, they seemed to suggest that exposure to very low levels of these chemicals, such as might occur when a bee fed on a treated oilseed rape crop, was not sufficient to kill many bees, but it seemed to affect their behaviour, particularly their ability to learn, gather food, and navigate. These are not impacts that are assessed by any of the safety tests by which pesticides are judged (although there are plans to introduce such tests in Europe in the very near future). They are also impacts that are likely to be much more important in the field, when bees naturally perform astonishing feats of navigation and learning when gathering food from flowers. It seemed to me, and to a number of other researchers around the world, that there was a need to study what impacts these sublethal affects might have on bee colonies in natural situations.

To investigate this, we exposed bumblebee nests to the concentrations of neonics found in the pollen and nectar of oilseed rape for two weeks, and then placed the nests out in the field to see how they fared compared to control nests. Over the following 6 weeks the treated nests grew more slowly, and ultimately produced 85% fewer new queens. Since our study, work from other labs has confirmed that field-realistic doses greatly reduce pollen collection in bumblebee workers, potentially explaining why our treated nests performed poorly. It has also been found that concentrations of neonicotinoid as low as 1 part per billion (ppb) in their food cause a drop in egg laying in bumblebees of 30%. Considerably higher concentrations than this have been found in pollen of treated crops (the typical range in pollen is about 1-10 ppb, although 50 ppb has been found in lucerne pollen, and over 100 ppb in melon pollen).

For bumblebees, the evidence so far is convincing and coherent; exposure to levels of neonic commonly found in crops have profound impacts on colony success. The only study which apparently contradicts this was recently placed online by Defra, a report describing a study they conducted in 2012 in which they attempted to repeat our work but with the pesticide exposure phase of the experiment occurring in the field. They placed bumblebee nests next to the only untreated field of oilseed rape they could find, or next to one of two other fields treated with two different neonics, and they followed the colonies over time. Unfortunately they had no replication – just one field per treatment – and, disastrously but interestingly, the control nests all became contaminated with neonics. The summary of this report claims the study shows no clear effect of neonicotinoids on bumblebee colonies; hardly surprising, given the absence of any controls – and hardly the sort of convincing evidence one would wish government to base its policies upon. It is also not really true – in fact there was a highly significant negative relationship between neonicotinoid levels recorded in each nest and how well the nest performed, but the authors removed this relationship by “taking out outliers” – by which they mean removing the nests that received the highest exposure (which also happened to be the nests that performed most poorly) from their data set and then re-ran the tests.

Perhaps the most valuable lesson to be learned from this work is that bumblebee nests placed into the English landscape become contaminated with multiple types of neonic, even when on farms where none are used. Many of the nests had concentration of neonic higher than 1 part per billion, and most had detectable levels of at least two different neonics.  Bizarrely, the results suggest that bumblebees have a particular predilection for the neonic thiamethoxam, for the control bees seemed to have ignored the untreated rape field right next to their nests and flown a long way to find a thiamethoxam-treated crop.

While the debate has focussed heavily on bees so far, there are broader issues to consider. Neonics are very persistent in soils, and evidence has recently emerged that they accumulate over time; a study in East Anglia performed by Bayer in the 1990s found concentrations up to 60 parts per billion in soil after 6 years of annual use. This is likely to be enough to have profound impacts on soil life. It has also emerged that they get into field margin vegetation, and into streams and ponds. A concentration of just 0.6 parts per billion is enough to kill mayfly nymphs. It may be that, while focussing on bees, we have missed the bigger picture. 


The economics

A common argument in favour of neonics is that they provide huge economic benefits, and that the alternatives are worse. A glossy document produced by the “Humbolt Form” (funded exclusively by the agrochemical industry) in early 2013 claimed that a ban on neonicotinoids would cost the EU 17 billion Euros and 50,000 jobs. However, the hard evidence for these claims seemed to be lacking. Indeed, the evidence that neonicotinoids are important for crop production is surprisingly difficult to find. Studies from USA show that yields of soya bean do not benefit at all from neonic seed dressing, despite their application being standard practice. Sadly, similar experiments in the UK have not been conducted. Since farmers get most of their agronomic advice from companies that supply pesticides, it is reasonable to suppose that a good proportion of UK pesticide use may be unnecessary.


Whatever happened to IPM?

When I was at University in the 1980’s, I read Rachel Carson’s Silent Spring, and was taught about the terrible mistakes made in agriculture in the 1950s and 1960s when indiscriminate use of persistent, broad-spectrum insecticides, and an abandonment of traditional cropping practices such as rotations led to huge pest outbreaks. The pest insects had all become resistant, while their natural enemies had largely been eradicated. As a result, an approach called Integrated Pest Management (IPM) had been developed, and we were taught that this was the future of pest control. IPM is predicated on minimising pesticide use: farmers monitor their crop pests, and only take action when necessary; they encourage natural enemies as far as possible, use crop rotations and other cultural controls to suppress pests, and only use the insecticides as a last resort. Even then, they avoid those that persist in the environment.

Whatever happened to this philosophy? Why are we now applying pesticides prophylactically to more or less all crops? Did we learn nothing from our past mistakes?  


The politics

The EFSA spent 6 months evaluating all the evidence, and concluded that current use of neonics poses unacceptable risks to bees. The UK’s Environmental Audit Committee (a group of MPs) agreed. Numerous NGO’s, including the RSPB, who are normally very cautious, also agree. Even the WI support a ban. What was once a radical stance is now where the vast majority of informed opinion lies; on 29 April the EU member states voted for a 2 year moratorium on use of the three most-commonly used neonics on crops visited by bees.

The UK voted against the ban, with Chief Scientific Advisor Sir Mark Walport saying that everyone else had misinterpreted the evidence. He also argued that applying the precautionary principle would lead us to continue using neonicotinoids, an argument that few of us could follow.


What Next?

The moratorium is only for two years, yet we have clear evidence that it will take far longer than this for neonicotinoids that have accumulated in soils to break down. In any case, they are still being widely used, on winter wheat for example, and some types of neonic are not included in the ban.  So it is unlikely that we will see the benefits of the moratorium in rebounding bee populations any time soon. In any case, there seems to be no plan to actually monitor bee populations, so even if they did recover it is not clear how we would know.

What will farmers do without neonics? It is hard to say. It would be nice if they returned to an IPM approach, but with their main / only source of advice being from people with a vested interest in selling chemicals, this seems unlikely. 


Have we solved the bees’ problems?

I’m afraid the answer is an emphatic NO. Bees have been declining for many decades, and much of their decline has been due to loss of flower-rich habitat, which has been exacerbated by the arrival of non-native diseases, and by widespread use of pesticides. We have taken a step to reduce (but not remove) their exposure to some brands of one type of pesticide, for two years. That is nowhere near enough. If we want to ensure healthy populations of honeybees, bumblebees, and other wild pollinating insects upon which we depend for our crop production, and more generally if we wish to support the healthy, diverse ecosystems upon which our future health and wellbeing depends, then we need to find ways to produce food in a sustainable way which incorporates the needs of biodiversity. At present we are failing to do this.


Dave Goulson's research lab website


Biggest bumblebee poisoning event in history



On 15 June, a landscaping company in Wilsonville, Oregon, decided to spray some lime trees with insecticide. The trees were in a parking lot, and had some aphids on them, so there was a risk that some cars might get little drops of sticky honeydew on them. Faced with such a dire threat to the future of humanity, it was only natural and reasonable that the company should blitz the trees with Dinotefuran, a type of neonicotinoid insecticide.

On 22 June, Saturday morning shoppers reported the car park to be blanketed in dead bumblebees; about 50,000 at the latest count. The trees were flowering, and bees love lime nectar. The dose of pesticide they received from the nectar was clearly enough to kill many of them almost instantly, for they fell dead beneath the trees, the biggest recorded bumblebee poisoning event in history. Perhaps many more staggered off to die elsewhere.

For me, this highlights the utter stupidity of allowing pesticides to be used for cosmetic purposes, in gardens and parks. Using pesticides in farming can be justified by the need to grow food efficiently; we all need to eat. But do we need to be able to pop to the local garden centre or supermarket and buy bottles of highly toxic compounds advertised for use on roses and other flowers? In towns, councils routinely spray herbicides and insecticides for no real purpose, other than to make the streets look a little tidier, or the grass in the park look a little greener (and a little more toxic).

Why don’t we ban pesticides in urban areas, and turn our cities into havens for wildlife?

Toronto has banned such chemicals within the city limits. The city hasn’t been over-run with pests. People still have pretty gardens, and grow healthy vegetables. The parks look just fine. If they can do it, why not the rest of us?

Back in Oregon, the Xerces Society, an organisation devoted to insect conservation, have attempted to enclose the poisoned limes with netting to keep bees out. But they are concerned that the poison may stay in the trees for years, since neonicotinoids are very long lasting, so they may poison bees for years to come.

One wonders how many similar incidents escape attention because the bees do not die in such an obvious place. “Wild bees are killed all the time in agricultural fields where nobody sees it happen,” said Mace Vaughan of the Xerces Society. “The fact that this happened in an urban area is probably the only reason it came to our attention.”

Isn’t it high time we stopped poisoning our bees?



USA finally considering action over neonicotinoids, spurred on by doubts as to whether they actually work



Two US Congressmen have launched a bill to suspend uses of neonicotinoid insecticides in the US, following the lead of the European Union. Representatives John Conyers of Michigan and Earl Bluemenauer or Oregon introduced the “Saving America’s Pollinators Act”. They were prompted by widespread honeybee colony losses and a major bumblebee kill in Oregon where 50,000 dead bumblebees were found beneath two lime trees as a result of their being sprayed with neonicotinoids for ornamental reasons (note that lime trees often have a few dead bumblebees under them for separate reasons that have never been fully explained). I was recently invited over to speak in Capitol Hill in support of this bill.   

The debate over neonicotinoids and bees rolls on and on, with new studies emerging every day. It seems to me that the evidence on bumblebees is clear and convincing - realistic doses are very likely to be doing harm to wild colonies – but the evidence for honeybees remains muddier. However, most of the studies finding no impact on honeybees have been funded by or performed by the industry that manufactures the chemicals, so murky waters are to be expected. 

My visit coincided with the launch of a fascinating review of the economic value of neonicotinoids, produced by the Centre for Food Safety, a US-based non-profit organisation. They review 19 studies that have evaluated how much neonicotinoid seed dressings (the usual way of using these chemicals) increase yield of a range of crops, including wheat, corn, soya beans, and oilseed rape. The findings are astonishing – in every case, the studies either found no benefit whatsoever, or weak and inconsistent benefits unlikely to offset the cost of the pesticide. As Dr Christian Krupke (a leading researcher on this topic at Purdue University) said to me, “There may be places in the US where the pests are so bad that farmers need neonicotinoid seed dressings, but we can’t find them”.

In short, the most widely used pesticides in the world - prophylactically applied to arable crops across the globe - appear to be ineffective, and to have been widely miss-sold. It reminds me a little of the Payment Protection Insurance scandal – farmers are advised to use seed dressings as an insurance against something which, it seems, almost never happens.

Remarkably, no similar studies seem to have ever been performed in the UK or elsewhere in Europe to evaluate how much, if at all, neonic seed dressings increase yield here. It would be easy to do – experimental plots of crops that are treated exactly the same, except for the presence or absence of the seed dressing. How did these chemicals come to be so widely used without the manufacturers demonstrating clearly that they worked? If they did perform such studies, why can nobody find them? Sceptics such as I might also point to Italy, where neonics were banned on corn some years ago and where yields have remained stable and corn farming profitable.   

For me, this turns the whole bee debate on its head. If neonic seed dressings were essential to grow crops, one might have to accept a risk of harm to bees. But it seems that they are not.

In Europe, a decision will need to be made in the next year or so as to whether the current EU moratorium is extended or allowed to lapse. This new evidence will hopefully help to prevent the latter.

Prof Dave Goulson, University of Sussex.

[An abbreviated version of this Blog is published in the newsletter of the BBKA, June 2014]

“Bee Informed” – but not by this propaganda




Pop in to your local Homebase, find the long aisles where the plethora of garden pesticides are arrayed, and you will now find glossy leaflets prominently displayed with a picture of a bumblebee on the front, entitles “BEE INFORMED - WHEN USING INSECTICIDES IN YOUR GARDEN”. So far so good, I can’t really argue with that. But read on.

Inside the leaflet, you will learn that bees are important. Excellent stuff. Then you will be told that bee health has been compromised, and that “A number of culprits have been identified, including:

• Parasitic mites such as Varroa

• Bacterial, fungal and viral diseases

• Habitat loss and degradation

• Genetic factors”

All true, but you might be thinking that there is an obvious omission from this list. Read on, and you will learn that “Some claims have also been made of a possible link between the decline in bee populations and the use of some insecticides. This has not been shown scientifically”. Hmmm.

The “some insecticides” they refer to are presumably neonicotinoids, the controversial chemicals that have been at the heart of a ferocious debate for ten years or more. Neonicotinoids are the active ingredient in many garden insecticides, and you may well also drip them on the neck of your dog or cat to prevent fleas. A group of scientists at the European Food Standards Agency spent six months examining the safety of these chemicals, and concluded that they pose an “unacceptable risk”. As a result, a majority of European countries voted for a ban on several of the most widely used neonics on flowering crops that bees might visit (the UK government opposed, of course). Since then, a huge review of over 1,000 scientific papers was written by 28 scientists from all over the world (I was one), under the auspices of the International Union for the Conservation of Nature, and it concludes that neonics are harmful to bees and pose a serious threat to biodiversity. On top of that, The European Academy of Sciences published a huge report on the subject last year, written by a team comprising a leading scientist from every European state. Their findings echoed the earlier reviews; these chemicals are damaging to bees and other wild insects. None of this is particularly surprising; these are highly poisonous neurotoxins that kill insects of any sort in minute, near-infinitesimal doses. They are also highly persistent, sometimes lasting for years in soil and plants.       

So who produced this wildly misleading leaflet? The Crop Protection Association, the Horticultural Trades Association, and the British Beekeepers Association (BBKA). The first two come as no surprise; these are essentially wings of the agrochemical industry, pushing their poisons as usual. But the BBKA? Really? Shame on you.

The leaflet goes on to say that “Provided that garden care products are used as directed on the label, they will not pose a problem to bee health.” Yet a recent Swedish study, published in the most prestigious scientific journal in the world (Nature), showed huge impacts of neonics on bumblebees and solitary bees when the chemicals were used by farmers ‘as directed on the label’. Remember that, 50 years ago, the agrochemical industry assured us the DDT was safe, until it turned out that it wasn’t. Later, they told us that organophosphates were fine, except they weren’t. Do you believe them this time? I don’t. 

The simple truth is that none of the array of chemicals on sale in your local garden centre are necessary. I have a two acre garden that I manage singlehandedly, while having a full-time job, and I manage to grow heaps of flowers and veg. It isn’t the tidiest garden ever, but it looks wonderful (to me anyway!). Every year my broad beans are attacked by a horde of black bean aphids, but after a week or two an army of ladybirds, hoverflies, lacewings and tiny parasitoid wasps come to the rescue, and in no time they are gone. The bean plants look a bit dog-eared, but they recover and give a great harvest. No need for insecticides. I’m ashamed to admit I used to use glyphosate, and I still have an old pot of it in the shed still, but since the World Health Organisation announced that it is highly likely to be carcinogenic[1] I have stopped using it. Hoeing works just fine, and I have kids and pets in the garden.   

To be honest, I expect nothing else from the pesticide industry. They are a hugely powerful and rich lobby that spends a fortune trying to convince us that we need their products. But why does Homebase push their propaganda? I guess money is the answer. Why does the BBKA support it? Do their members agree? I’m pretty sure that most of them don’t. The senior management of BBKA have always had an oddly cosy relationship with the agrochemical industry, to the horror on many of the BBKA members who I have spoken to. I guess that money has changed hands at some point.

The leaflet also mentions the Royal Horticultural Society as a source of further information, though it is not clear if RHS endorse it. I sincerely hope not.

We should boycott Homebase until they stop displaying this leaflet (my boycott started today, but on my own I don’t think that will bring them to their knees). We should campaign for these chemicals to be withdrawn entirely from garden use. I would love to see ALL pesticides banned for use in the garden; there is just no need, no need at all.  


The leaflet can be downloaded from the Crop Protection Association directly here:


[1] Glyphosate, a herbicide, is the most widely used pesticide in the world. It is in most foods we eat. Recent studies have found significant levels of glyphosate in urine of almost every German of 2,000 tested, with the highest levels in children.