Health Canada says seed coated with imidacloprid, an insecticide known as a neonicotinoid, does not pose a risk to bee health.
Scientists with the Pest Management Regulatory Agency, which oversees agricultural pesticides, released a preliminary report today on imidacloprid and its potential impact on pollinators.
The agency said there was “no potential risk to bees,” from seed treated with imidacloprid, a Bayer product sold under the name Gaucho.
However, the U.S. Environmental Protection Agency in its release chose a different emphasis. It said imidacloprid was a problem, but only above certain residue levels, which occur mainly in cotton and citrus crops.
“Other crops such as corn and leafy vegetables either do not produce nectar or have residues below the EPA identified level,” the EPA said in its release.
“Additional data is being generated on these and other crops to help EPA evaluate whether imidacloprid poses a risk to hives.”
The report was a joint release between the PMRA and EPA. The national regulatory bodies, along with the State of California, have collaborated on a pollinator risk assessment for foliar, soil and seed treatment uses of neonicotinoids on agricultural crops.
The PMRA said its part of the study found no negative impact for bees.
“The data set available to assess risk from treated seed included residue information in pollen, nectar or flowers of Canadian relevant crops, Tier II tunnel studies and Tier III field studies specific to seed treatment applications. Available higher tier tunnel-studies and field studies with seed treatments did not result in notable effects on bees,” the preliminary report said.
“The residue levels in crop pollen and nectar resulting from seed treatment uses are typically below levels expected to pose a risk to bees at both the individual bee and colony levels.”
Almost all of the corn and canola seed in North America and most of the soybean seed is coated with a neonicotinoid seed treatment. The three most common neonics, as they’re commonly known, are imidacloprid, thiamethoxam, a Syngenta product branded Cruiser and clothianidin, a Bayer product known as Poncho.
The agencies launched the assessment a few years ago after multiple scientific studies found that neonics adversely affect bee behaviour, cause bee deaths and compromise colony health. For instance, several studies concluded that neonics interfere with pollinator navigation, as bees exposed to the insecticide had trouble finding their way back to the hive.
PMRA and EPA scientists were seeking an answer to a basic question: can approved uses of imidacloprid affect pollinators?
The EPA said, in a release, that imidacloprid is a threat to bee hives when imidacloprid residues on a crop reach 25 parts per billion.
“Above which effects on pollinator hives are likely to be seen… below (that level) effects are unlikely,” the EPA said. “These effects include decreases in pollinators as well as less honey produced.”
EPA scientists said imidacloprid residues are most likely to exceed the 25 ppb threshold on cotton and citrus crops.
As for foliar application in Canada, the PMRA said the risk from foliar application during crop bloom was low because product labels prohibit applications during bloom for most bee attractive crops.
Pre-bloom application may pose a risk to bees but the agency only had residue data for crops grown outside of Canada.
A University of Saskatchewan study found that neonicotinoids can accumulate in soil and can be detected in ponds near agricultural fields. The PMRA agreed that imidacloprid is persistent in the environment.
“In treated fields, imidacloprid has been shown to carry over from one growing season to the next. When imidacloprid is used for multiple years in succession, concentrations in soil initially increase and then stabilize after approximately three years.”
The PMRA also concluded that imidacloprid is “routinely” found in rain puddles, which are known sources of drinking water for pollinators.
The EPA plans to release preliminary risk assessments for other neonicotinoids in December.