Study counters reports of seed treatment-bee link

Ontario field study | Researchers unable to link insecticide exposure and bee colony health

A comprehensive field study conducted last summer near Guelph, Ont., found no link between insecticidal seed treatments and bee health.


The findings are in contrast to European reports suggesting insecticides are destroying bee colonies across the globe,


Researchers are still reviewing the Ontario data, but the evidence shows that canola treated with clothianidin, a Bayer neonicotinoid, is not a threat to bee colony health, said Cynthia Scott-Dupree, a professor in the University of Guelph’s School of Environmental Sciences.


“From the data that I’ve seen, I’m not seeing any effect of exposure … to canola treated with clothianidin,” said Scott-Dupree, who led the field study with Chris Cutler of Dalhousie University.


Bees exposed to the insecticide produced virtually the same amount of honey as a control group of bees, said Scott-Dupree.


“A reduction in honey yield is an indication of overall poor colony health. If the pesticides are having an impact, the bees are not going to be foraging.”


The study comes at a time when European Union countries are banning or considering restrictions on three popular neonicotinoids: clothianidin, thiamethoxam and imidacloprid. Studies released last year in France demonstrated that bees exposed to thiamethoxam, a Syngenta product better known as Cruiser, were twice or three times as likely to die while foraging because they couldn’t find their way back to the hive.


A Scottish study demonstrated that colonies exposed to imidacloprid, a Bayer insecticide, produced 85 percent fewer queens than the control group.


The studies, subsequent reports and newspaper headlines compelled European politicians to respond.


The European Commission recommended that EU countries prohibit the use of the three neonicotinoids in seed treatments and crop application for two years beginning this spring. 


Bayer funded Scott-Dupree’s canola study at a cost of $950,000 in an effort to produce field scale data on clothianidin and its impact on bee health.


“That’s huge. That’s (for) a one year study,” she said. “Last year it was the largest bee project that (Bayer) had going globally.”


Scott-Dupree and eight employees placed 40 bee colonies in 10 canola fields near Guelph last summer. Five canola fields had seed treated with clothianidin and five fields did not. The fields were 10 kilometres apart and five acres in size.


The hives were placed in the middle of the canola fields at 25 percent canola bloom, and the bees foraged on the canola for two weeks. 


Following exposure, the 40 colonies were moved to a military site near Meaford, Ont., on a peninsula that extends into Lake Huron, to ensure the bees wouldn’t forage on crops treated with neonicotinoids for the remainder of the summer.


Scott-Dupree measured three factors besides honey production: bee deaths, weight gain of colonies while foraging on canola, and insecticide residue on bees and in pollen, nectar, beeswax and honey.


Scott-Dupree said she couldn’t share much information about insecticide residue because scientists at a U.S. Department of Agriculture lab are examining and analyzing samples taken during the study. 


“I’m not (aware) of all the residue data, but I do know that all our samples collected while bees were at the (military site) … were free of all neonicotinoid residues.”


The research team also spent $30,000 on photography equipment to document colony health throughout the experiment, taking 12,000 images during the trial.


“We used digital photography to assess the amount of field brood and the number of adults on all frames in the colony,” she said.


“There is software … that will actually determine the amount of field brood and amount of adults on all those frames.”


The research team hasn’t yet analyze all the photos.


The U.S. Environmental Protection Agency and Canada’s Pest Management Regulatory Agency, which oversaw and signed off on the field study protocols, requested the photography work.


Scott-Dupree said she knows critics will say she’s in Bayer’s back pocket or focus on the study’s weaknesses when it is submitted for publication later this year, even though the EPA and PMRA verified the protocols and an independent quality assurance team supervised data collection and analysis. 


“I know that this research is done at a very high level,” she said.


“I think when people read it, instead of accepting the results, they (will) look for the gaps and what the negatives are. ‘Well, you didn’t do this.’ ”


The difficulty performing field studies on honeybees will be a potential criticism.


“Unfortunately, the colony is so incredibly complex in regards as to how it interacts with chemicals in the natural system,” said Chris Mullin, an entomologist who studies pesticides and pollinator health at Penn State. 


“You can do all you want about trying to umbrella the beehive in a field situation, that they can’t forage beyond a certain point…. But that’s not how it works in real life…. The field studies are almost impossible.”


However, Scott-Dupree said policy- makers and the media shouldn’t focus solely on laboratory studies of neonicotinoids and bees. 


“The importance of these field studies is substantial because a lot of the critical data indicating that neonics are killing the bees is based on laboratory studies,” she said. 


“The doses the bees are exposed to (in lab studies) are far above what a realistic field dose exposure would be…. What those studies prove is, yes, neonicotinoids are toxic to bees. Am I surprised? No. They are insecticides and bees are insects.”

  • Researchers haven’t analyzed all the data, but early results indicate 
there is no impact on bee health at field level doses.

  • Hives comprising bees that foraged on canola grown with clothianidin treated seed produced 52.8 kilograms of honey, while the control group produced 51 kg. Average Ontario honey yield in 2012 was 37 kg.

  • There was no difference in colony weight gain between bees exposed
to clothianidin and the control group.

  • Dead bee counts, done over four assessment dates during canola 
bloom, showed 140 dead bees in hives exposed to clothianidin 
and 133 dead bees in the control group.

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