Bumblebees are less able to start colonies when exposed to neonics, putting them at risk of extinction, Canadian researchers report.
University of Guelph professor Nigel Raine says when exposed to a common neonicotinoid pesticide, the chances of a bumblebee queen starting a new colony plummet.
“Bumblebee queens that were exposed to the neonicotinoid were 26% less likely to lay eggs to start a colony,” says Raine, holder of the chair in pollinator conservation.
“A reduction this big in the ability of queens to start new colonies significantly increases the chances that wild populations could go extinct.”
Published in the journal Nature Ecology & Evolution, the study was conducted with researchers from Royal Holloway University of London, England/
Neonicotinoids are among factors contributing to the decline of bees and are being phased out or restricted in a number of countries including Canada.
The researchers examined the impacts of exposing the queen bumblebees to thiamethoxam in spring when they emerge from hibernation and are preparing to lay their first eggs and establish a colony.
“Given the vital role spring queens have in maintaining bumblebee populations, we decided to focus on assessing the impacts at this stage in the life cycle,” Raine says.
“These spring queens represent the next generation of bumblebee colonies.”
More than 300 queen bees were exposed to environmental stressors common in the field including parasite infections. About half of the queen bees that successfully emerged from hibernation were then fed syrup treated with pesticide at levels similar to those found in wild pollen and nectar for two weeks.
The researchers then recorded the bees’ egg-laying behavior and mortality rates for another 10 weeks.
“We observed the queens to see whether low level pesticide exposure might lead to changes in these important nesting behaviors,” Raine says. “When a queen is going to set up a colony, she will secrete wax and form it into containers for nectar and pollen. She will then begin to lay her eggs and sit on them like a bird.”
The queens exposed to pesticides laid 26% fewer eggs and, using a mathematical model, the researchers found this rate of decline could threaten extinction of wild bumblebee populations.
“We urgently need to know more about how pesticides could be affecting other species to make informed decisions about the risks associated with using these chemicals,” Raine says.