by SUSAN MANN
The Ontario government is moving full steam ahead to reduce provincial farmers’ neonicotinoid use next year and beyond despite new science showing one type of the insecticide, clothianidin, used on seeds for canola crops poses a low risk for honeybees.
A recently published study by University of Guelph environmental sciences professor Cynthia Scott-Dupree and Dalhousie University environmental sciences department associate professor Chris Cutler of the neonicotinoid, clothianidin, concluded honeybee colonies face a low risk foraging on canola crops grown from seeds coated with the pesticide.
Asked about the study and its possible effect on the ministry’s plans, Ontario Agriculture, Food and Rural Affairs Minister Jeff Leal says by email the ministry is working with beekeepers, grain farmers and others in the farming sector “to identify tangible ways to reduce the use of neonicotinoid-treated seed for the 2015 growing season.” The government is also “committed to developing a system that requires the targeted use of seed treated with neonicotinoids” to be in place by July 1, 2015. That gives “farmers enough time to transition for the 2016 growing season.”
Leal says Premier Kathleen Wynne supports the ministry’s plans as outlined “in her mandate letter to me.”
The ministry is also continuing its work on a comprehensive pollinator health plan to address the many other aspects of pollinator health, Leal says.
For 2015, the ministry is working with Grain Farmers of Ontario to distribute the "Guide to Early Season Field Crop Pests." The ministry is also promoting best management practices and placing ads in farm publications that talk about the need to use untreated versus treated seeds. The ministry plans to hold public consultations on its plans to have a system in place reducing neonicotinoid-treated seed use for the 2016 growing season.
The conclusion reached by Scott-Dupree and Cutler is just a small piece of the picture on one particular crop, says Peter Kevan, University of Guelph professor emeritus. And that’s why the study does not resolve the question of sub lethal effects of neonicotinoids on bees and pollinators, he says. “We know there are sub lethal effects of neonicotinoids on bumblebees (because of previous studies done). They (neonics) have, of course, lethal effects.”
Kevan says the study’s conclusion applies to a very specific instance. “You cannot go from that straight to other neonicotinoids, other crops and pollinators in general.”
But Kevan says the science in the study is sound. The study was funded by Bayer CropScience, he says, but “Bayer would not have any bearing on the results.”
In a notice with the study the researchers noted Bayer personnel did not have a role in collecting or interpreting field and honeybee colony data or in writing the manuscript.
Cutler also says the study doesn’t lay to rest the question of sub lethal effects. “There’s still uncertainty. In the paper we acknowledge that because some of our control samples of pollen had clothianidin, that’s a problem with the experiment. But it doesn’t mean you should slam the book shut and say the study is useless.”
In addition, the study won’t stop the controversy swirling around neonicotinoid use, but Cutler says he’s comfortable putting bees next to a canola field grown using clothianidin-treated seeds.
The study was done during the summer and autumn in 2012 in 10 southwestern Ontario fields. Plantings in half the fields used treated seeds while the other half, the control fields, used untreated seeds.
Forty honeybee colonies were divided between the two field types. They came from the Arkell Agricultural Research station, according to the study published in an on-line scientific journal called PeerJ, and were placed in the fields when 25 per cent of the canola was in bloom.
“The presence of 25 per cent bloom ensured that bees would not forage off site, as would occur if colonies were moved to fields before bloom,” the study says.
Cutler says they used canola for their study “because it’s a very attractive source of forage for bees.” The scientists were interested in discovering if bees’ dietary exposure to nectar or pollen obtained from plants grown using neonicotinoid-treated seeds pose a hazard to bees.
“People think that science proves things and that’s not the case,” he says. “We never prove things; we just try to confirm or refute hypotheses.” The hypothesis in this experiment was bees exposed to canola during bloom that’s grown using clothianidin-treated seeds “suffer no effects,” he says.
The colonies were removed from the fields after 14 days and transported during darkness to an isolated apiary located on a Canadian Forces military base near Meaford about 165 kilometres northeast of Guelph. As far as the study’s researchers know, “this site was isolated from any crops grown from seeds treated with neonicotinoids by about 10 kilometres.” At this site, the bees forged on a variety of wildflowers.
The bees were moved to the military base because “if we exposed them to something after the canola during bloom we’d have a potential problem with the experimental design,” Cutler says.
The colonies from the control fields were separated from the colonies from the clothianidin-treated fields. In September 2012 the colonies were moved at night to a winter apiary located at the University of Guelph’s Arkell Agricultural Research Station.
Cutler says they intended to leave the bees in the canola fields for the entire usual three- to four-week canola bloom period but the summer of 2012 was hot and dry. That meant the canola bloom only lasted for about 2.5 weeks. “But nonetheless we still got high exposure.”
The researchers collected pollen the bees were bringing back to the hives. “During peak bloom, almost 90 per cent of the pollen being brought back was canola pollen,” he says.
The study results suggest that exposure to canola grown from clothianidin-treated seed didn’t adversely affect honeybee colonies. There were no significant differences between colonies placed on treated sites compared to control sites for hive weight gain and honey production. The number of dead bees recorded in front of hives during the summer was low and normal. The number of adult bees and amount of sealed brood did not differ between treatments. Overwintering success also didn’t differ between treatment and control groups, the study says.
Residue analysis indicated honeybees were exposed to low levels of clothianidin in pollen of 0.5 to 1.9 parts per billion, the study says.
Researchers did not detect clothianidin in residues of nectar, honey or beeswax, the study says. But low levels of clothianidin were detected in pollen samples toward the end of the canola plants’ bloom in some of the control sites. The source of the pesticide in pollen from those sites is unclear, the study says. It does, however, show the “difficulty of conducting a perfectly controlled field study with free-ranging honeybees in agricultural landscapes.”
Cutler says it’s not unusual to not detect clothianidin residues in nectar, honey or beeswax. “Some people are under the perception you’ll always detect it and that’s absolutely not true.”
The study also says although various laboratory studies have reported sub lethal effects in individual honeybees exposed to low levels of neonicotinoid insecticides “the results of the present study suggests that foraging on clothianidin seed treated crops under realistic conditions poses low risk to honeybee colonies.”
Overall, colonies were vigorous during and after the exposure period and “we found no effects of exposure to clothianidin seed treated canola on any end point measures,” the study says.
In Ontario, canola is grown on 30,000 to 70,000 acres annually compared to the 1.9 million acres seeded to corn this year and the three million acres seeded to soybeans. And there’s no doubt neonicotinoid seed treatments are valued by farmers. A North American study of corn, soybean and canola growers done by independent agricultural economists concluded the value of neonicotinoid seed treatments for Canadian and American farmers is among the highest of all insect management practices with a total farmer value of $1.4 billion. The second most valued practice was Bt corn at $1.3 billion, followed by foliar insecticides at $306 million and soil insecticides at $175 million.
The provincial beekeepers’ association and the organization representing pesticide manufacturers have different opinions on the Scott-Dupree/Cutler study’s validity.
Pierre Petelle, vice-president, chemistry for CropLife Canada, says the study is groundbreaking and lays to rest the question of sub lethal effects of neonicotinoids on bees and pollinators. “These types of studies are very large scale, very comprehensive and very costly to conduct” with this one costing close to $1 million.
Petelle says the difference between the Scott-Dupree/Cutler study and others are most of the others are done in labs where bees are exposed to neonicotinoids and researchers look for negative effects. But “we’ve said all along this is an insecticide and bees are insects. If you expose them to unrealistic doses of course it’s going to have an effect.”
But the Scott-Dupree/Cutler study done under real life conditions with crops grown using products as farmers would use them found neonicotinoid-treated seed “is not a route of exposure of concern for bees.”
Tibor Szabo, Ontario Beekeepers’ Association first vice president, says he doubts the researchers had a true control group of bee colonies.
The Arkell research station is two kilometres from his home bee yard. In 2012, there were massive bee kills during spring planting “and I had colonies dropping dead right in that location,” he says. “Part of the official documented bee deaths of 2012 occurred within two kilometres of the Arkell research station, so it’s very likely to assume any of those bees (used in the study) would have already been exposed to clothianidin or the other neonic seed treatments.”
Cutler says they didn’t detect clothianidin in the first week of the experiment. “There’s a table in the paper showing all the other pesticides we detected and they (the bees) are actually pretty clean.” The bees were strong and doing well. “Our honey yields were over 50 kilograms per hive, that’s 15 kilograms more than the Ontario average.”
About criticisms of the study, Cutler says they knew they’d have “some issues with the experiment. I think it was as good as we could make it. I think it was objective.” In addition, all the “data was audited.” Quality assurance people went into the fields and watched as workers in the study collected data. “There was a high level of scrutiny involved in the study.”
In addition, during the study the researchers had an open field day for beekeepers, Health Canada and provincial government officials to see the work and suggest improvements, he says. “We incorporated those suggestions.”
Meanwhile, on Monday the Canadian Association of Physicians for the Environment and the Registered Nurses Association of Ontario added their voices to the issue by calling for a ban on all neonics. BF