Two studies show that a class of chemicals known as neonicotinoids created disorientation among bees and caused colonies to lose weight, which may have contributed to a mysterious die-off.
Two new studies released on Thursday show that industrial pesticides -- specifically chemical neurotoxins called 'neonicotinoids' -- have robust negative impact on the honey bees' ability to navigate and sufficiently reproduce. Previous studies have shown that insecticides may play a role in 'colony collapse disorder,' a term that describes huge bee die-offs in recent years, the direct and specific cause of which has remained elusive to scientists, but these studies are unique for being conducted in the field as opposed to in laboratory conditions.
"People had found pretty trivial effects in lab and greenhouse experiments, but we have shown they can translate into really big effects in the field. This has transformed our understanding," Prof David Goulson, at the University of Stirling and leader of one of the research teams told The Guardian. "If it's only one metre from where they forage in a lab to their nest, even an unwell bee can manage that."
One scientist, who lauded the study for its role in furthering understanding of the bees decline, also noted that the study should aware the public that these same chemical pesticides could be having similar impacts on other species as well. "There's a general phenomenon of pollinator decline — bats, bird, butterflies, all kinds of things," he said.
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From Science Magazine: Field Research on Bees Raises Concern About Low-Dose Pesticides
Five years ago, bees made headlines when a mysterious condition called colony collapse disorder decimated honey bee colonies in parts of the United States. Now bees are poised to be in the news again, this time because of evidence that systemic insecticides, a common way to protect crops, indirectly harm these important pollinators. Two field studies reported online this week in Science document problems. In bumble bees, exposure to one such chemical leads to a dramatic loss of queens and could help explain the insects' decline. In honey bees, another insecticide interferes with the foragers' ability to find their way back to the hive. Researchers say these findings are cause for concern and will increase pressure to improve pesticide testing and regulation.
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“It’s pretty damning,” said David Goulson, a bee biologist at Scotland’s University of Stirling. “It’s clear evidence that they’re likely to be having an effect on both honeybees and bumblebees.”
Neonicotinoids emerged in the mid-1990s as a relatively less-toxic alternative to human-damaging pesticides. They soon became wildly popular, and were the fastest-growing class of pesticides in modern history. Their effects on non-pest insects, however, were unknown.
In the mid-2000s, beekeepers in the United States and elsewhere started to report sharp and inexplicable declines in honeybee populations. Researchers called the phenomenon colony collapse disorder. It was also found in bumblebees, and in some regions now threatens to extirpate bees altogether.
Many possible causes were suggested, from viruses and mites to industrial beekeeping practices and climate change. Pesticides, in particular neonicotinoids, also came under scrutiny.
Leaked internal reports by the Environmental Protection Agency showed that industry-run studies used to demonstrate some neonicotinoids’ environmental safety were shoddy and unreliable. Other researchers found signs that neonicotinoids, while they didn’t kill bees outright, affected their ability to learn and navigate.
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The Guardian report adds:
The pesticides investigated in the new studies - insect neurotoxins called neonicotinoids - are applied to seeds and flow through the plants' whole system. The environmental advantage of this is it reduces pesticide spraying but chemicals end up in the nectar and pollen on which bees feed. Goulson's group studied an extremely widely used type called imidacloprid, primarily manufactured by Bayer CropScience, and registered for use on over 140 crops in 120 countries.
Bumblebees were fed the toxin at the same level found in treated rape plants and found that these colonies were about 10% smaller than those not exposed to the insecticide. Most strikingly, the exposed colonies lost almost all of their ability to produce queens, which are the only bee to survive the winter and establish new colonies. "There was a staggering magnitude of effect," said Goulson. "This is likely to have a substantial population-level impact."
The French team analysed the effect on honey bees of a new generation neonicotinoid, called thiamethoxam and manufactured by Syngenta. They fitted tiny electronic tags to over 650 bees and monitored their activity around the hive. Those exposed to "commonly encountered" levels of thiamethoxam suffered high mortality, with up to a third of the bees failing to return. "They disappeared in much higher numbers than expected," said Henry. Previous scientific work has shown insect neurotoxins may cause memory, learning, and navigation problems in bees.
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Jeff Pettis of the Department of Agriculture's bee research lab in Beltsville, Md., who wasn't involved in the studies, praised the bumblebee report in particular for highlighting that honeybees aren't the only ones that may suffer from sublethal doses of pesticides. He predicted that the effects on bee reproduction would raise red flags for regulators at the Environmental Protection Agency.
"There's a general phenomenon of pollinator decline — bats, bird, butterflies, all kinds of things," he said.
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