Report finds neonicotinoid insecticide used at the correct time does not compromise bee colony health
Health Canada has decided that laboratory experiments don’t count for much, at least when it comes to bees.
In a report released in early January, the Pest Management Regulatory Agency said seeds treated with imidacloprid, a neonicotinoid insecticide, pose no risk to bees.
“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,” the report said.
It was part of a joint release with the U.S. Environmental Protection Agency and the State of California, which are collaborating on a pollinator risk assessment for foliar, soil and seed treatment uses of neo-nicotinoids.
Almost all of the corn and canola seed in North America and most soybean seed is coated with a neonicotinoid.
The three most common neonics are imidacloprid, sold as Gaucho by Bayer, thiamethoxam, a Syngenta product branded Cruiser, and clothianidin, another Bayer insecticide known as Poncho.
The agencies launched the assessment a few years ago after multiple studies found that neonics affect bee behaviour, cause bee deaths and compromise colony health. For instance, lab experiments discovered that neonics interfere with pollinator navigation because bees exposed to the insecticide had trouble finding their way back to the hive.
Scott Kirby, director with the PMRA’s environmental assessment directorate, said agency scientists did consider Tier 1 laboratory experiments on neonics, but those studies can tell only so much. He said laboratory studies on bees are comparable to testing for gas mileage on a treadmill.
“It (the lab) is very controlled, but it’s also very unnatural.”
Instead, PMRA scientists relied on the results of Tier 2 and Tier 3 experiments on neonic seed treatments.
“Higher tier tunnel studies and field studies with seed treatments did not result in notable effects on bees,” the report said.
Some pollinator experts claim field studies on bees have limited merit because controlling the environmental variables of foraging bees is too complex.
Leonard Foster, a University of British Columbia biologist who studies bee genomics, said such criticism is ridiculous because most scientific experiments have complex variables.
“If you take the position that it’s too complex … then I guess you’re not going to believe anything (a) scientist tells you,” he said.
“At some point you have to believe what has been done in the Tier 3 studies…. Those kind of studies … are more telling of real world status than Tier 1 studies.”
Cynthia Scott-Dupree, a University of Guelph environmental scientist who has conducted field studies on neonics and bees, said Health Canada took the opposite approach of the European Union, which banned the use of neonic seed treatments in 2013.
“I am feeling very positive … that the PMRA is considering Tier 2 and 3 studies in the final determination of risk,” she said.
“In other situations (EU decision), the Tier 2 and 3 studies were not considered and the final decision was based primarily on Tier 1 lab results.”
EPA and PMRA scientists determined that imidacloprid does compromise bee colony health when residue levels on crops reach 25 parts per billion.
Residues can exceed that level when imidacloprid is applied as a foliar spray to citrus crops and cotton.
“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 a news release.
As for crop residues in Canada, the PMRA said the risk of exceeding 25 p.p.b. is unlikely during foliar application. Product labels prohibit applications during and before bloom for orchard fruits and bee attractive crops.
“The conclusions on both sides of the border are the same. There are some foliar uses that produce levels (which) are potentially problematic for bees,” Kirby said.
“For the foliar uses, we (Canada) … have mitigation in place that basically protects bees.”
The PMRA plans to release a comprehensive preliminary pollinator assessment on imidacloprid, with appendices, Jan. 18. It will then accept public comments on the report for 60 days.