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expert reaction to possible link between neonicotinoid seed coating and bee colony losses

The use of neonicotinoid pesticides continues to be an area of heated debate, and a paper published in the journal Scientific Reports has reported a correlation between loss of honey bee colonies and use of a particular neonicotinoid in England and Wales, as well as a possible economic benefit to farmers who were able reduce subsequent insecticide applications.


Prof. Nick Birch, senior entomologist and IPPM expert, James Hutton Institute, said:

“The new paper raises a number of interesting points on trade-offs between prophylactic seed treatments (used in advance of pest pressure knowledge) and use of sprays or alternatives (based on pest monitoring and pest thresholds during the growing season). Farmers willing to pay a premium for an insurance treatment in advance to stabilise yields, if the cost is not too great and there are crop protection AND/or yield stability benefits.

“The data on yield responses presented is quite variable across years; this is normal when weather patterns, pest pressure and crop agronomy are less predictable. The data on regional imidacloprid use and honeybee colony loss shows at best a weak positive relationship (the scatter of data points is high, especially at the two extremes). Both these points indicate that longer term studies are needed, to tease apart the other factors that are known to affect bee colony health, behaviour and multi-season pollinator survival. A recent EFSA working group concluded that bees are exposed to multiple stressors at landscape scale so the development of more realistic spatially explicit models and long term monitoring projects are urgently needed around Europe.

“We and other scientific groups are working with industry and farmers to select biopesticides which can suppress pests like aphids and are compatible with pollinators and natural enemies, reducing risks for both farmers and the environment (eg AHDC SCEPTRE project on fruit, vegetable and ornamental crops). This will lead to new IPPM (Integrated Pest and Pollinator) strategies for UK and European crops. These IPPM systems take several years to develop and test, so in the meantime farmers need environmentally-friendly crop protection measures to reduce their risks, stipulated by current EU crop protection policies.”

Prof. Felix Wäckers, Lancaster Environment Centre, Lancaster University, said:

“The paper by Budge et al addresses the costs and benefits of using neonicotinoids. They uniquely use large long-term datasets to test for possible correlations between the use of this group of pesticides and both bee mortality and crop yield. It is shown that the incidence of bee colony failure is higher in areas in which neonicotinoids are used more intensively. This provides important field evidence confirming earlier results of negative bee impacts in controlled studies.

“Correlations between the use of the neonicotinoid imidacloprid and crop yield and farming profits were less clear-cut. While there were positive correlations in some years, the correlations were actually negative in another and no overall positive effects on yield or farmers profits were seen across the years.

“Unfortunately, the (political) debate on the banning of neonicotinoids seems to be increasingly reduced to cost-benefit calculations. Having said this, the present paper makes an important contribution by substantiating this economical discussion with some actual data. While the negative impacts on honeybees are clearly highlighted by this study, the actual impact on wild pollinators (which are considerable more sensitive to this group of insecticides) remains underexposed. Given the important role of these wild pollinators, their decline and its ecological impact as well impact on crop pollination will have to be taken into account.”

Dr Richard Gill, Lecturer, Imperial College London, said:


“It is important to consider that ‘hazard’ and ‘risk’ are not the same things. Previous scientific studies looking at the detrimental effects of neonicotinoids shows they can be hazardous to non-target organisms such as pollinating insects. Such studies have subsequently fuelled opinion that neonicotinoids pose an unacceptable risk to bees.

“Many previous studies have focused on manipulating exposure in experimental setups that may not represent realistic field conditions. We actually know relatively little about the levels of exposure to bees in the real world.

“Furthermore, scientific evidence is mixed, with some studies finding no detectable effects on bees when exposing them to neonicotinoids at levels approximating field realistic concentrations, and they often do not consider dosage – which describes the amount of the chemical actually coming into contact with the bee.”

This study:

“This study by Giles Budge and colleagues takes a valuable and novel approach to addressing the risks of neonicotinoids to honeybees. They found that the application of neonicotinoids as a seed treatment to oilseed rape can reduce the number of applications of other pesticides, such as pyrethroids, which are known to also be hazardous to wildlife.  On the other hand, one notable result of the study found that there was a slight positive relationship between the use of just one neonicotinoid, Imidacloprid, and the proportion of honeybee colonies recorded to be lost by beekeepers. However, we should note that the study shows a correlation between Imidacloprid use and honeybee colony losses, not causation.

“Whilst Budge and colleagues show a correlation with Imidacloprid use and honeybee colony losses, they found no association with two other neonicotinoids, Clothianidin and Thiamethoxam. It is possible that because the use of Clothianidin and Thiamethoxam has only increased in the past few years (and was only considered in 2010 for this study), we do not see any association, but we also know that in the UK the use Imidacloprid has reduced significantly.

“Their work should be applauded as they importantly take a balanced approach by considering both the costs and benefits to farming practices and honeybee health from neonicotinoid application to regions across the UK over a decade (2000-2011). Whilst the authors do find some evidence that could question the efficacy of neonicotinoid seed treatment in certain years, it does highlight that application can provide benefits to framing practices as well.

“The large scale of their datasets gives the evidence more weight than past individual studies. However while the authors take into account a large set of environmental variables, there may be other unforeseen factors that have not been accounted for. Therefore, whilst we must take these results seriously we must also understand the limitation of correlative studies.

“When assessing the value of neonicotinoid application it is important to consider both the benefits and costs to society and to wildlife. We should consider all the evidence and not focus solely on the detrimental effects if we are to sustainably use pesticides to ensure food security for the future.”


Prof. David Goulson, Professor of Biology (Evolution, Behaviour and Environment), University of Sussex, said:

“Although many experiments in the lab or field have found negative impacts of neonicotinoids on bees, this is the first to provide evidence for large scale impacts on honeybee colony losses across an entire country. It should be noted that the study particularly implicates imidacloprid, but that the authors were not able to test for similar impacts of other more recently introduced neonicotinoids such as thiamethoxam or clothianidin because these chemicals have not been in use for sufficiently long to allow this kind of analysis to be performed.

“It is interesting that the study found no benefit of imidacloprid for crop yield, echoing similar reports from the USA and Canada (for soya bean) which suggest that neonicotinoid seed dressings are often used in situations where they provide no measurable benefit to the farmer.”


Dr Christopher Connolly, Reader in the Medical Research Institute at the University of Dundee, said:

“The study by Budge et al makes an important new contribution to the debate over the risk to bees from the neonicotinoids. The good news is that the use of imidacloprid-coated OSR seeds reduces the subsequent need for autumn spraying of insecticides. Sadly, this use does not reduce the spraying in spring, during flowering, when bees are providing pollination services.

“Despite farmer’s fears, there appears to be no widespread benefit to crop yield in the use of imidacloprid over the use of insecticidal sprays. Therefore, the choice of insecticide should be more about their relative risk to the environment and the need to circumvent emerging pest resistance to insecticides.

“The authors correctly point out that their findings should not be extrapolated to the use of the other neonicotinoids, clothiandin and thiamethoxam, as small differences in their chemical structure can exert major differences in their toxicity.

“Moreover, caution is needed in the interpretation of this study. Although it demonstrates a convincing correlation between honeybee losses and the use of imidacloprid, it does not demonstrate cause and effect. For example, according to the FERA website ( the use of fungicides, herbicides, insecticides sprays and molluscicides on OSR have all increased in the last 7 years, so other chemical hazards also exist. Nevertheless, I believe that the combined evidence (laboratory and field) against the use of imidacloprid on pollinator visited crops is now very strong.”

Dr Peter Campbell, Head of Research Collaborations, Syngenta, said:

“I welcome the use of these large-scale real-world datasets to evaluate the impacts of a range of factors on honeybee colony health. The authors clearly identify regional effects and the importance of external factors such as the spring weather in colony loss; this is not surprising as spring is an important time for honeybee colonies rearing brood to replace over-wintered bees and for colony expansion. They also identified a correlation with imidacloprid use but not when other NNI seed treatments were included. Given the major change in the use profile of the NNI seed treatments in oilseed rape in the UK since 2010 it is an open question whether the correlation existed post-2010.  As the authors highlight these data were not derived from a controlled experiment, and so colony loss may be influenced by other confounding factors not accounted for in their models. These factors  include Varroa and associated viruses, beekeeper management practices and the diversity of other forage sources throughout the season. It is clear from these data that neonicotinoid seed treatments have a significant benefit to farmers in pest control and reduce the need for autumn applied insecticide sprays, as highlighted by the crop losses in autumn 2014.  The authors call for a  large-scale study on the real-world impacts on pollinators of the use of neonicotinoid seed coatings on mass flowering crops, this is currently underway in Germany, Hungary and the UK  co-ordinated by CEH and will provide further large –scale data to inform the debate.”


Evidence for pollinator cost and farming benefits of neonicotinoid seed coatings on oilseed rape’ by name of G. E. Budge et al. will be published in Scientific Reports at 14:00 UK time on Thursday 20th August 2015, which is also when the embargo will lift. 


All our previous output on this subject can be seen at this weblink:


Declared interests

Prof. Nick Birch, Prof. Felix Wäckers and Dr Richard Gill: none received.

Prof. Goulson: nothing to declare

Dr Christopher Connolly: “I am lead applicant on a Biotechnology and Biological Sciences Research Council, the Department for Environment, Food and Rural Affairs, the Natural Environment Research Council, the Scottish Government, and The Wellcome Trust, under the Insect Pollinators Initiative (United Kingdom) Grant BB/1000313/1​.”

Dr Peter Campbell: “I am employed by Syngenta.”

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