Neonicotinoids are supposedly highly targeted insecticidesbut now they are turning up in the pollen of poppies, blackberries and hawthorn blossom in hedges, at levels that high enough to cause harm to bees.
Scientists at Sussex University have discovered that bees are exposed to a toxic chemical cocktail when feeding from wildflowers growing next to neonicotinoid treated crops in UK farmland.
The findings are published today in a paper in the journal Environment International, 'Widespread contamination of wildflower and bee-collected pollen with complex mixtures of neonicotinoids and fungicides commonly applied to crops' by Arthur David et al.
The research by Sussex University and supported by the Soil Association reveals that pollinators consuming pollen from these crops or from nearby wildflowers will ingest a cocktail of fungicides and insecticides.
"In summary, our study confirms that bees foraging in arable farmland are exposed to a complex cocktail of neonicotinoid insecticides and fungicides in the pollen they collect", they conclude.
Dave Goulson, Professor of Biology at the University of Sussex, and one of the authors of the paper, said: "It is clear that insects visiting wildflowers in field margins are chronically exposed to a cocktail of chemicals.
"The effects that this has on their health have never been studied, and there is an urgent need to do so. In the meantime, the precautionary principle would suggest that we should take steps to reduce this exposure as much as possible."
One result is that honey from bees in urban areas is actually much cleaner than that from the countryside, at least in areas where arable crops are grown.
"Pesticide levels in pollen gathered in urban areas were much lower, but still contaminated, demonstrating both the value of the urban environment and need to minimise garden pesticide use", commented Dr Christopher Connolly of the School of Medicine at the University of Dundee.
The countryside is now a dangerous place for bees!
One in ten species of Europe's wild bees is facing extinction, and neonicotinoid insecticides are increasingly seen as contributing to these declines. In addition to neonicotinoids, farmers may spray some non-organic crops a dozen or more times while they are growing, with anything up to 23 different chemicals.
The wild flowers found by researchers to be contaminated by neonicotinoids and other toxic sprays included: Creeping Buttercup, Bramble, White Campion, Scented Mayweed, Hogweed, Hawthorn, Poppy, Wild Rose, Burnet Saxifrage and Fool's Parsley.
"Overall, these results and other similar studies in France and the USA indicate that these mixtures of insecticides and fungicides appear ubiquitous in pollen samples and that even higher concentrations than the ones observed in our study can be encountered", the authors write.
"For both species [honey bees and bumble bees], pollen from hawthorn represents a major part of the collected pollen (up to 87%) and that the pollen from hawthorn collected by honey bees was often contaminated by several pesticides (up to six) and notably at concentrations up to 29 ng/g for carbendazim."
A prior study also suggests fungicides can act synergistically with other pesticides, making the insecticides up to 1,000 times more deadly than they are on their own. (See References)
Peter Melchett, Policy Director of the Soil Association, added: "These findings are shocking. Neonicotinoids are supposedly highly targeted insecticides yet the researchers have found that they are turning up in the pollen of poppies, blackberries and hawthorn blossom in hedges, at levels that on their own are enough to cause harm to bees.
"Worse still, they are present along with a whole cocktail of chemicals, some of which could increase the toxicity of neonicotinoids up to 1,000 times."
UK's 'safe havens' policy doomed to failure
To combat bee decline, the UK Government's Pollinator Strategy has focused on creating 'safe havens' for bees by increasing flower habitats next to fields - yet this research shows these flowers may be laden with dangerous chemicals.
As a result, says Melchett, the government must urgently rethink its strategy, which already appears doomed to failure: "The UK government must act. Until now, the government's main solution to the bee crisis is to pay farmers a small chunk of the £900 million Common Agricultural Policy (CAP) money, available to help wildlife, to create flower rich habitat next to crops.
"Yet this research suggests that these supposedly safe havens for bees are actually potentially dangerous chemical cocktail bars. These flower margins must be protected with a full ban on neonicotinoids; the current EU ban is only partial, and in the UK mainly applies to just one crop - oilseed rape. Neonicotinoids are still used on other crops, for example on over 25% of all UK cereals. Neonicotinoids will be poisoning the field margins of many of these crops.
"We also want to see the government finally setting out a strategy for reducing pesticide use in farmland - as is required by EU law. This has always been the gaping hole in the government's strategy to save our bees".
And in fact, the impact of the pesticides on bees could be even worse than revealed by this study, which examines only the pollen gathered by bees:
"While quantifying realistic levels of exposure via pollen as we have done here is an important step forwards, we did not examine exposure via nectar, which we intend to address in future work", the study notes. "A major challenge which has yet to be tackled is attempting to understand what effects simultaneous exposure to multiple pesticides has upon bees in the field."
Earlier work highlighting the dangers of neonicotinoids has been criticised for exaggerating the concentrations of the pesticides that pollinators would encounter in farmed lanscapes - and the authors take the opportunity to put the record straight:
"Experimental studies such as Whitehorn et al. (2012), which describe severe impacts of neonicotinoids on bumble bees, have been criticised for using unrealistically high concentrations of pesticide (in this example 6 ng/g of imidacloprid) (Carreck and Ratnieksi 2014).
"Our data suggest that real-world exposure may often be much higher than this, for the mean concentration of thiamethoxam in our samples from 5 nests located in farmland was 18 ng/g, and one of the nests located in urban environment showed more than 19 ng/g for imidacloprid.
"It has also been demonstrated that there are synergies between neonicotinoids and DMI fungicides such as flusilazole (Iwasa et al., 2004; Schmuck et al., 2003), so the presence of both compounds at high concentrations in pollen stores of bumble bees is a cause for concern."
Dr Connolly, who was not involved in the research, observed: "Validating semi-field studies on neonicotinoids (artificial provision of pesticide) requires confirmation that bees do actually get exposed to these levels of pesticide in the field where multiple sources of pollen and nectar exist. This study provides such a bridge to validate previous studies.
"Furthermore, of the 20 pesticides examined, most OSR pollen samples contained 7-12 different pesticides, whilst pollen gathered by honeybees and bumblebees contained 2-10 pesticides. This does not represent the full pesticide load, only a reflection on the few examined.
"The work by David et al is very important as, although in Europe, farmers are legally obliged to keep pesticide use records (EC No. 1107/2009), the data are not collected and so scientists have no access to local cocktail use. Therefore, studies like this should help governments realise the potential importance of gathering this information."
Oliver Tickell edits The Ecologist.
The paper: 'Widespread contamination of wildflower and bee-collected pollen with complex mixtures of neonicotinoids and fungicides commonly applied to crops' by is published in the journal Environment International.
Principal source: Soil Association.
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Iwasa T, Motoyama N, Ambrose JT, Roe MR. 'Mechanism for the differential toxicity of neonicotinoid insecticides in the honey bee', Apis mellifera. Crop Prot. 2004;23:371–378.
Schmuck R, Stadler T, Schmidt HW. 'Field relevance of a synergistic effect observed in the laboratory between an EBI fungicide and a chloronicotinyl insecticide in the honeybee (Apis mellifera L, Hymenoptera)', Pest Manag Sci. 2003;59:279-286. [PubMed]