The NFU is calling for an independent and comprehensive assessment of the existing evidence surrounding the impact of neonicotinoids, after Buglife issued a report claiming they are partially responsible for the decline in bumblebee populations.
Buglife, a trust dedicated to the conservation of invertebrates, wants to see the use of all UK products containing neonicotinoids — which is currently used on a range of horticultural crops including top and soft fruit, brassicas, peas and potatoes — put on hold, pending a review of this group of insecticides.
The Soil Association, Pesticide Action Network and Bumblebee Conservation Trust are backing its calls - which follow the publication of the report The Impact of Neonicotinoid Insecticides on Bumblebees, Honey Bees and Other Non-Target Invertebrates.
The report was submitted to Number 10 Downing Street on 9 September during discussions on how to reverse the bee decline.
It collates research from a variety of organisations from across the globe, including Defra, the European Food Standards Authority and the Journal of Economic Entomology.
Buglife concludes that neonicotinoids damage the health and life cycle of bees as they spread throughout the plant and into the nectar and pollen that bees then eat. This then makes them forage less and produce fewer offspring.
Chief executive of Buglife Matt Shardlow said: "This is the most comprehensive review of the scientific evidence yet and it has revealed the disturbing amount of damage these poisons can cause to bees - it is now time for Hilary Benn to act.
"It is clear from this review that the process is inadequate regarding risks to bees, as it fails to properly test for a range of sub-lethal effects and potential poisoning routes that are likely to affect bee populations in the UK countryside."
Soil Association policy director Peter Melchett added: "The UK is notorious for taking the most relaxed approach to pesticide safety in the EU; Buglife's report shows that this puts at risk pollination services vital for UK agriculture."
The NFU, however, said that Buglife's claims were based on selective case studies that had not thoroughly assessed the impact of neonicotinoids.
NFU horticulture adviser Dr Chris Hartfield, who joined the group of invited experts at Number 10, said: "Buglife's call for a suspension on the use of neonicotinoids is not backed by any of the key beekeeping organisations in the UK.
"To tackle bee health problems effectively, we believe we need to work on the basis of what we know, not what we suspect. Although the report adds a useful perspective to the debate, the fact of the matter remains that there is still no clear evidence that the use of crop-protection products containing neonicotinoids is a factor causing the worrying honeybee losses we are experiencing across the UK.
"All pesticides undergo a rigorous approval process based on sound science and we would expect sound scientific arguments to be presented before the withdrawal of any product was considered.
"What the debate really needs is an independent and comprehensive assessment of the situation to inform the process."
Bee farmer and Bee Farmers' Association of the UK (BFA) secretary John Howat added: "The fact is that the parasitic mite Varroa is a major pest killing honeybee colonies - and our controls for it are failing. Why do we need to divert our attention from this danger?"
The reduced resistance of honeybees caused by Varroa infection makes them more susceptible to other problems such as viruses, bacterial diseases and possibly crop-protection chemicals. But for the BFA, the evidence is far from clear. "Until there has been a thorough and unbiased review of all the evidence, which takes account of the quality of the evidence and the relevance of it to honeybees in the field, we are not prepared to call for any ban."
Howat also raised concerns about what alternative products would be used if neonicotinoids were banned. As a relatively new product, it is likely they would be replaced by older chemistry that could be of greater risk to bees.
The number and diversity of male partners a queen honeybee has could help to protect her children from disease, scientists at the University of Leeds claim.
The researchers are working on the theory that the reason some colonies are wiped out while others remain healthy could be down the genetic diversities of the hives.
Dr Bill Hughes, from the Faculty of Biological Sciences at the University of Leeds, said: "By making sure queens mate with enough genetically variable males, we may be able to boost resistance levels and so protect our honeybee populations from disease attacks like the ones we have seen hitting the US."
One possibility is that the number and variety of potential mates for a queen is becoming too low to maintain genetic diversity and therefore disease-resistant populations.
Hughes added: "Given the choice, queen honeybees will typically mate with up to 12 different male partners in a matter of minutes and some with over 20."
The Leeds scientists will be examining the question of genetic resistance by studying honeybee reactions to a common fungus parasite called chalkbrood, under carefully controlled laboratory conditions.
The fungus, already found in the majority of UK hives, infects and "eats" larvae, giving them a chalky appearance. Individual larvae die, but the parasite rarely kills the whole colony. In 2008, US average losses of honeybee colonies were 35 per cent.
The project, which has received just under £500,000 in funding from the Natural Environment Research Council, is due to last for three years.
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