University of Guelph researcher Ryan Norris thinks neonicitinoid seed treatments on corn are reducing hatch of eggs that Monarch butterflies lay.
Although it’s only a three per cent reduction, he said it’s significant because it could total millions of larvae.
“It’s the first field evidence that neonics can have a negative impact on larval survival of monarchs,” Norris told CBC News.
Monarchs, which migrate every year between Canada and Mexico have prompted many studies because their numbers have declined by more that 80 per cent over the last two decades.
Norris’s findings are published in the Journal of Animal Ecology outlining how they worked with a farmer near Halton who planted one half of a small plot with corn seed that had only been treated with a fungicide and the other half treated with clothianidin, a common neonic.
Milkweed was deliberately planted along with the corn to attract monarchs.