Neonicotinoids impede bumblebee egg production

Another study shows pollinator pesticide impacts

A common bumblebee visits a garden in Vienna, Austria. @bberwyn photo.

Staff Report

It’s no secret that various pesticides are killing bees in many different ways, despite all the lies from chemical companies trying to make you think otherwise. In that battle for truth, and ultimately justice, more science helps, and researchers from the University of Guelph have show now systemic neonicotinoids reduce egg production in wild queen bumblebees.

“Queen bees will only lay eggs when the eggs are fully developed,” said Prof. Nigel Raine, holder of the Rebanks Family Chair in Pollinator Conservation. If queens need to use energy to clear pesticides from their system instead of investing in eggs, then fewer fully developed eggs will result, he said. “This will likely translate into slower egg-laying rates, which will then impede colony development and growth.”

The study is the first to link exposure to thiamethoxam — one of the most commonly used neonicotinoid pesticides — to fewer fully developed eggs in queens from four wild bumblebee species that forage in farmland.

The findings have been published in the journal Proceedings of the Royal Society B.

Neonicotinoids are one of a number of factors contributing to the decline of bees and are currently being phased out or restricted in several countries including Canada. The European Parliament is scheduled to debate and vote on restrictions next month.

The researchers studied now queen bumblebees are affected by exposure in the spring when they emerge from hibernation and are preparing to lay their first eggs and establish a colony.

The emergent spring queen bees represent the next generation of bumblebee colonies. Worker bees from those first eggs are needed to clean and guard the nest, find food and tend to the next batch of eggs. Without those workers, the colony will likely fail, said Raine.

For the study, about 500 queen bees from four species were caught in early spring and for two weeks were fed syrup treated with pesticide doses similar to levels found in pollen and nectar in the wild. They were then observed for another two weeks before they were frozen, dissected and examined.

The researchers found that across all four species the queen bees that were given higher doses of thiamethoxam had smaller, less-developed eggs than the queens not exposed to the pesticide.

Raine suspects the metabolic costs associated with the detoxification required from pesticide exposure results in a reduced amount of nutrients available for other biological processes such as egg development.

The researchers also found queen bees from two of the four species ate less nectar after being exposed to thiamethoxam.

The fact that queen feeding behavior was impacted by exposure to thiamethoxam in only two of the four bee species highlights the reality that sensitivity to pesticides differs among bee species, Raine said.

“Most of the work to determine levels of toxic exposure to pesticide has used honeybees as a model pollinator. But our findings show that bee species vary in their level of sensitivity to pesticides, which is important information that should be factored into regulatory decisions on these chemicals.”


3 thoughts on “Neonicotinoids impede bumblebee egg production

  1. Reasoning is about the same as with humans, actually. Pollutants, primarily insecticides, and plasticizers are blamed for a decrease in fertility and both egg and down production in US.

  2. Earlier studies have shown that pesticide exposure can reduce the production of bumblebee queens by as much as 80%. Now this study shows that those surviving queens may have reduced egg laying.
    This story doesn’t seem to grasp what this may actually mean. Can you imagine the Colorado high country without our world famous wildflower bloom? Honey bees can’t survive on their own much above 7,500 feet. High attitude wildflowers are completely dependent on the bumblebee family for pollination because only the bumblebees can survive the winters at altitude. If we begin losing the bumblebees there’s little doubt that it will affect the Colorado wildflowers.

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