A University of Guelph scientist will try to answer a question this summer that is perplexing entomologists in Europe and North America: are canola seeds treated with insecticide killing bees?
Cynthia Scott-Dupree, a professor in the university’s School of Environmental Sciences, will release bees onto a blooming canola field near Guelph to determine if coating seeds with clothianidin, a Bayer Crop Science insecticide, harms bees’ health.
Beekeepers and environmentalists have claimed that clothianidin, a neonicotinoid insecticide, kills bees.
In March, U.S. beekeeper associations and environmental groups filed a petition, with 1.25 million signatures, asking the U.S. Environmental Protection Agency to ban clothianidin.
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Field trials with pollinators are tricky because it’s difficult to control how and where bees gather nectar and pollen. However, Scott-Dupree said her study will follow strict protocols because representatives of the EPA and the Health Canada’s Pest Management Regulatory Agency have reviewed the experimental methodology.
“I would say this particular study (is being) done under GLP (Good Laboratory Practice)…. Every step is independently quality assured by quality assurance officers,” she said.
“This level of science should be beyond scrutiny because it’s (being) checked at every level, comprehensively.”
Getting the study right became more significant in early June after France banned Cruiser OSR, a Syngenta insecticide and fungicide seed treatment for canola.
The decision was based primarily on a French study released this spring that showed exposure to thiamethoxam, the insecticide in Cruiser, interfered with the bees’ navigational and homing systems. In short, bees exposed to a low dose of the chemical couldn’t find their way back to the hive.
The French ban wasn’t a shock because studies published over the last two years have demonstrated that neonicotinoids can hamper bee reproduction, navigation and cause death, said Peter Kevan, a U of G ecology professor and entomologist.
“I believe that the neonicotinoids have been implicated in enough situations in Europe, the U.S.A. and now in Canada that they need to be evaluated as to the risk they pose to pollination, pollinators and beekeeping,” said Kevan, who heads up a Canadian research network on pollinators called Canpolin.
Neonicotinoid seed treatments are particularly concerning because the chemicals are systemic, meaning they invade plant tissue and contaminate the pollen and nectar of plant flowers in small quantities.
Jonathan Lundgren, a U.S. Department of Agriculture entomologist in Brookings, South Dakota, said it’s hard to assess how the French ban will affect seed treatment policies in North America.
However, he said more research is needed to determine if seed treatments are harming beneficial insects.
“Seed treatments have come on very quickly, and they’ve been adopted very quickly by farmers in North America,” he said. “There is not a lot of information out there, independent research, on the idea of how these insecticidal seed treatments are affecting non-target species.”
Scott-Dupree said her field study, which is funded by Bayer, won’t evaluate neonicotinoids’ impact on individual bee activities, such as flight and navigation. Rather, she wants to understand how feeding on canola plants grown with clothianidin-treated seed affects overall colony health.
“We’re not looking at minor behavioural differences,” said Scott-Dupree, who grew up in Brandon.
“We’re looking at things that beekeepers would also do to make their assessments.”
Following the canola bloom, Scott-Dupree will check the bees for brood production and adult mortality. After over-wintering, they will count the number of adults and evaluate the hives for colony strength.
Scott-Dupree carried out a similar study in 2007 on canola treated with clothianidin, which was published in the Journal of Economic Entomology. The paper found no difference in bee mortality, brood development and worker longevity between the experimental group and the control group.
“The results show that honeybee colonies will, in the long term, be unaffected by exposure to clothianidin seed-treated canola,” Scott-Dupree wrote in 2007.
However, the EPA no longer accepts the conclusions of that study. The agency decided the canola fields were too close together, which meant bees may have migrated between fields rather than remain on the seed treated canola fields.
Scott-Dupree altered the protocols for her latest field trial to accommodate the EPA’s criticism.
“In this study that we’re doing this year, all fields are separated by 10 kilometres.”
Scott-Dupree knows entomologists and environmentalists from around the world will scrutinize her study, but she said she has confidence in the protocols and hopes the result will influence public policy in North America.
“I would like this study … to stand in the foreground in the decision making by EPA and PMRA, in terms of what they think the kind of impact that neonicotinoid seed treatments are going to have on bees.”
However, Scott-Dupree thinks that seed treatment policy will ultimately be based on public opinion and politics.
“In the end, I think politics and emotion outweigh the science. It has frustrated me over the last 15 years, that often when we have really good scientific evidence, people don’t listen to it.”
- neonicotinoids are the most widely used insecticides in the world
- this spring, scientists with the French National Institute for Agricultural Research published a paper, which showed that bees exposed to low doses of thiamethoxam, a Syngenta neonicotinoid, were two or three times more likely to die while foraging than a control group, because they couldn’t find their way back to the hive
- in another study, Scottish scientists treated bumblebee colonies with imidacloprid, a Bayer neonicotinoid. The colonies exposed to the insecticide produced 85 percent fewer queens than the control group, which the scientists concluded would significantly thwart colony reproduction
- in a Purdue University study, scientists found high levels of clothianidin and thiamethoxam in planter exhaust while planting seed-treated corn. Dead bees found near the entrances of hives in the spring had high levels of clothianidin. Scientists weren’t sure if the exposure was from contact with soil contaminated with planter dust or from pollen collected by bees.
