Comprehensive field studies carried out by Syngenta have found no evidence linking neonicotinoid seed treatments to poor bee health.
Restrictions on the use of three neonicotinoid pesticides on bee-attractive crops, including Syngenta’s thiamethoxam (Cruiser), will come into force across the EU from 1 December.
The European Commission pushed through a two-year ban on neonicotinoids despite a split among EU countries.
The action was in response to the European Food Safety Authority’s (EFSA) scientific opinion that these insecticides posed an unacceptable risk to bees.
The UK government said the scientific case for banning neonicotinoids, based largely on lab studies in which bees were exposed to much higher doses of pesticides than when they are in the field, had not been proven.
DEFRA secretary Owen Paterson said evidence that neonicotinoids harmed bees was “inconclusive”, adding that more research was needed at field level to justify a ban.
The results of a Food and Environment Research Agency (FERA) study, published in March, established that when used under field conditions within a normal agricultural setting neonicotinoids did not have a major effect on bumblebee colonies.
Now Syngenta has recently published the findings of its own field research carried out between 2005 and 2010 in different regions of France into the effects of thiamethoxam on bee health.
“This study clearly shows that exposure and hence risk to bees from thiamethoxam is much lower in the field, than under forced artificial conditions used in many published laboratory studies – some of which exaggerated the doses.”
Luke Gibbs, Syngenta UK spokesman
The study, published in the peer-reviewed journal PLOS ONE, investigated the long-term risk to honeybee colonies from four years of consecutive exposure to flowering maize and oilseed rape grown from thiamethoxam treated seeds at maximum recommended rates for insect control in Europe.
It looked at the impact on bee mortality, foraging behaviour, colony strength, colony weight, brood development, food storage levels and over-winter survival of honeybees.
However, it showed no difference between control hives and those adjacent to flowering crops treated with thiamethoxam.
Luke Gibbs, spokesman for Syngenta UK, said: “This study clearly shows that exposure and hence risk to bees from thiamethoxam is much lower in the field, than under forced artificial conditions used in many published laboratory studies – some of which exaggerated the doses.
“The exposure and risk is lower in field studies because residues of thiamethoxam in nectar and pollen from seed-treated crops are generally very low. Also under real field conditions bees have a choice where they forage and hence will forage on a range of food sources, not just a treated crop.”
Syngenta said the study was completed as part of a regulatory data package generated to support the application to use Cruiser as a seed treatment on maize and oilseed rape in the EU.
Mr Gibbs added: “We would have preferred to see this published sooner but, quite rightly, the journal’s review process is extremely rigorous and took almost a year to complete.”
Syngenta, Bayer CropScience and BASF have filed legal challenges with the European Court of Justice in Luxembourg to try and reverse the imminent ban on the use of their neonicotinoid-based pesticides.
The HGCA has warned that the ban on neonicotinoid seed treatments could cost UK growers at least £72m a year due to a lack of control of two key crop pests – cabbage stem flea beetle and aphid-spread turnips yellow virus.
Syngenta said field trials carried out this year at demonstration plots at Rougham in Suffolk had shown the consequences of not treating rape with a neonicotinoid insecticide seed treatment.
Simon Roberts, Syngenta’s field technical manager, said: “Cruiser OSR protected plots have continued to establish well, with strong plants at four to six true leaves that are well set for winter, at about 85-90 plants/sq m.
“The adjacent untreated plots, however, typically now have just 50 plants/sq m. Many of these plants are smaller and there is visibly greater insect pest damage on all leaves.”