A Health Canada study on neonicotinoid seed treatments has irritated beekeepers in Ontario and delighted defenders of the technology.
However, it’s probably premature to be outraged or to celebrate because Health Canada will release two more reports on neonicotinoids later this year.
The Pest Management Regulatory Agency, the U.S. Environmental Protection Agency and the State of California released a joint report Jan. 6 on imidacloprid, a Bayer insecticide.
Almost all of the corn and canola grown in North America and most of the soybeans are coated with a neonicotinoid. The three most common neonics are imidacloprid, sold as Gaucho, thiamethoxam, a Syngenta product branded as Cruiser, and clothianidin, another Bayer insecticide known as Poncho.
The government agencies initiated a pollinator risk assessment after multiple studies found that neonics affect bee behaviour, cause bee deaths and compromise colony health.
The agencies agreed that imidacloprid, when used as a seed treatment, is not a threat to honeybees.
“We did not have positive findings of risk for the seed treatment uses we assessed ,” the EPA said in an email.
“Residue levels in pollen and nectar appear below the threshold for effects on honey bee colonies.”
The Ontario Beekeepers Association challenged the findings, saying PMRA scientists used questionable methods and assumptions about seed treatments because the bulk of scientific evidence proves neonics are a threat to bees.
“We categorically reject any notion that overplanting of corn and soy and the overuse of seed treatments with neonicotinoids are not contributing to the ill effects on our industry,” said OBA president Tibor Szabo.
The association has convened its own panel of scientists to review the PMRA, EPA and State of California report.
The imidacloprid report will not be the final word on neonic seed treatments. The three government agencies will report on thiamethoxam and clothianidin later this year.
The risk assessments of those neonics are likely more relevant because they are more commonly used as seed treatments than imidacloprid.
These “newer” neonics may be more hazardous to bees.
“In general, clothianidin is considered to be more toxic to bee pollinators than imidacloprid. Clothiandin is a “second generation” neonic, and in all chemical classes advanced generations tend to be more toxic,” said Cynthia Scott Dupree, a University of Guelph environmental scientist who has conducted field scale studies on neonics and bees.
Her field experiments in Ontario indicate that clothianidin residues on canola are relatively low. In 2007, she found residues of 2.24 parts per billion in canola nectar and 2.59 p.p.b. in pollen.
“These residue amounts are much lower than the NOAEC (no observed adverse effect concentration) of 20 p.p.b. for clothianidin on honeybees,” Scott-Dupree said.
“The potential risk to pollinators of exposure to neonics in pollen and nectar of canola soybeans and corn is extremely low.”
The OBA will release its report on the Health Canada findings later this month.