New Field Tests Find These Pesticides Are Harming Bees
Amro Zayed checks out the progress of one of the frames from the hive. Image: York University


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New Field Tests Find These Pesticides Are Harming Bees

It’s long been suspected this was bad for bees.

I recently donned a white beekeeper suit and latex gloves to get acquainted with some honeybees at York University in Toronto, where 80,000 of these pollinating insects are kept on the rooftop of a campus building for research. Biologist Amro Zayed handed me frames, sticky with honey, covered in hundreds of buzzing insects.

We need bees to pollinate our crops, but it's no secret that bees are in danger in North America. It's been hypothesized that certain pesticides, called neonicotinoids or neonics, are harmful to these buzzing insects.


In a new paper, published today in the journal Science, Zayed and his co-authors investigated the idea, partly with these bees here at York. In two of what they say are the first large-scale, field-realistic studies to date, researchers from Europe and Canada (including Zayed) show that continuous, long-term exposure to neonics is harmful to bees.

Worker honeybees in a colony preparing the honeycomb for nectar. Image: York University

Since they were first discovered in the 1980s, neonic pesticides have become the most widely used class of insecticides in the world, and are applied to food crops, vet products, and even used in fish farms, according to a 2015 paper. Neonics interfere with brain signalling in the bee brain. This has an effect on worker bee behavior and mortality.

"Because the honeybee colony lives or dies on how well the worker behaves, workers exposed to neonics are unhealthy and they also make the colony unhealthy," Zayed said.

In Canada, neonics are widely used as seed treatments on major prairie crops. Environmentalists have been calling for a ban for a long time, and Health Canada is considering a ban on almost all uses of imidacloprid, one of several neonicotinoid pesticides. According to the CBC, they're set to issue a final decision by the end of this year.

Read More: Scientists Used a Little Bee Puppet to Teach Real Bees How to Play Bee 'Soccer'

In the new study, the team took 60 colonies and randomly allocated them to areas near corn, or areas adjacent to corn fields. Colonies were measured over an entire season. They found that neonic-treated colonies lost queens and weren't able to replace them effectively. The honeybees were monitored with a tiny RFID attached to their backs that let researchers know when bees left and returned to the colony, as well as when they weren't active and therefore probably dead.


A honeybee worker with a tiny RFID tag on its back helps researchers track when it enters and leaves the hive. Image: Amro Zayed

Meanwhile, researchers in Europe saw similar results. Scientists worked in Germany, Hungary, and the UK near oilseed rape crops treated with neonicotinoids.

Investigations into the effects of neonics on bee health has been going on for over two decades now, but it's been hard to pin down the exact effects, because bee populations are likely affected by all kinds of pressures, including climate change. Zayed and his co-authors found that when the workers and queen bees were subjected to neonics at levels that they would normally experience in the field, their life cycles were five days shorter. That doesn't seem like much, but worker bees only have a life cycle of about six or seven weeks, so that's like if you had 13 to 15 years cut off of your life.

Honeybee workers coming and going from one of the hives at York University. Image: York University

Zayed said he was surprised to find that bees were being exposed to neonicotinoids for three or four months of the year—longer than he had anticipated. "[This] is a very substantial and very surprising result," he said. "When people were talking about chronic exposure or long term exposure, they were talking about a week, a month, a month and a half."

Unfortunately, food crops treated with neonics aren't the only place where honeybees come in contact with the pesticide. Researchers found that pollen collected by bees coming from crops near a neonic-treated field were also contaminated. These are crops that hasn't been treated by the pesticide, but neonics spread through water and flowed into nearby crops.

"It's very tough being farmer. They have a tough job to do and certainly I don't want to prevent them from having access to effective chemicals and treatments that allow them to deal with pests in their crops," said Zayed. "I think we've shown that there is a cost to neonicotinoids. Pollinators, honeybees, bumblebees and native bees all suffer."

He's interested to see how new legislation around neonics impacts the bees. "If the legislation works, in a couple of years when we complete the experiment, we shouldn't find long term exposure to neonicotinoids and colonies should be healthier," he said.

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