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It’s Time for a Neonicotinoid Time Out

The views expressed are those of the author and are not necessarily those of Scientific American.


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There’s a mounting pile of evidence that three particular neonicotinoid insecticides, clothianidin, imidacloprid and thiamethoxam, are harming bees. During the late 1990’s this class of pesticides began being used to treat corn and other field crop seeds. Today, they are the most commonly used pesticides in the U.S., and have covered millions of acres.

Photo courtesy of C. Löser via Wikimedia Commons

Despite their omnipresence, their safety for pollinators is increasingly in question. And the proof keeps pouring in.

“It’s reached a point when it’s time for the Environmental Protection Agency to withdraw the registration of these pesticides until proven safe,” says Scott Black executive director of the Xerces Society for Invertebrate Conservation. “If things were done right, this information would have gotten to scientists and the EPA before [the pesticides] got to the market,” continues Black. “But, now we have enough data to conclude that there may be a substantial risk from these insecticides.”

Last month, the European Safety Authority (EFSA) announced that clothianidin, imidacloprid and thiamethoxam put bees at a ” high acute risk,” particularly through their contact with pollen, nectar and seed dust. The study is part of the impetus behind the EU’s upcoming March 15th vote on whether to ban the use of these pesticides on corn, oil seed rape, sunflowers and some other crops. The ban would be for two years.

It’s a ban that fell on the deaf ears in the U.S. last year. But, that was before more research. In March 2012, a study published in Science showed that neonicotinoid pesticide use hinders the growth of bumble bee colonies and reduces the number of new queens by 85%. Bad news for bumble bees.

“In honey bee colonies the large worker force gives the colony a buffer and while we have shown effects of neonics on individual bees, at the colony level we normally have not seen them,” wrote Jeff Pettis, an entomologist and researcher with the USDA, in an email. “The bumblebee studies do show a clear effect at the colony level.”

Another report shows that when bees are exposed to thiamethoxam at non-lethal levels, their homing system fails. Then there are people who believe we’ve only touched the tip of the honeycomb when it comes to the harmful effects of pesticides. One of these is Rusty Burlew, a beekeeper and bee enthusiast, who runs a website called honeybeesuite.

“Both field and laboratory testing on pesticides is done on adult bees and very little, if any, is done on the larval stages because it has not been required for registration,” wrote Burlew via email. “These chemicals, and others, are adversely affecting bees in the larval stage of development.”

Burlew adds that pesticide testing is done on a product-by-product basis, even though they are not used that way. Most pesticides are used in combination with others and synergistic effects are common. Not only that, but as the pesticides degrade they often produce metabolites that are more toxic to an organism than the original formulation. Like Black, Burlew believes these pesticides should be embargoed until proven safe.

“These pesticides should be banned until they are studied on all stages of bee development (especially the larval stage which is the most vulnerable), until the toxicity of pesticides used in combination with others is studied, and until all the pesticide metabolites are studied as well,” wrote Burlew. Only then can we make an informed decision.”

The question remains: what does the EPA think since it regulates the use of these chemicals? The EPA granted a conditional, or temporary, registration to clothianidin in 2003. The same approval was given to thiamethoxam. Imidacloprid was registered in 1994. It was not conditional. The EPA is now re-evaluating the safety of neonicotinoids. According to Scott Black, the EPA has stated that the registration review process will take several years. At the earliest , the new verdict for imidacloprid will be in 2016 and 2017 for clothianidin and thiamethoxam.

There’s one large caveat should the EPA rethink the registration of these neonicotionids: the replacement compounds need to be better, not worse.

Robynne Boyd About the Author: Robynne Boyd began writing about people and the planet when living barefoot and by campfire on the North Shore of Kauai, Hawaii. Over a decade later and now fully dependent on electricity, she continues this work as an editor for IISD Reporting Services. When not in search of misplaced commas and terser prose, Robynne writes about environment and energy. She lives in Atlanta, Georgia.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. rigg38a 5:06 pm 03/18/2013

    Aaaz has a webpage calling for support for the pesticide ban in the EU. It can be seen at
    http://www.avaaz.org/en/bye_bye_killers_uk/?tWnspeb
    Worldwide action needs to be coordinated so that the USA and EU both take action to prevent further and catastrophic bee death.

    Link to this
  2. 2. rigg38a 5:11 pm 03/18/2013

    Avaaz has a website calling supporters to petition the EU to prohibit use of the bee-killing pesticides. It can be seen at:
    http://www.avaaz.org/en/bye_bye_killers_uk/?tWnspeb
    Worldwide coordinated action could prevent catastrophic bee decline. The USA and EU have the opportunity to act; please remind them of their responsibility to the food supply and thereby to humanity.

    Link to this
  3. 3. emakovec 10:46 pm 03/19/2013

    Yes, Robynne, that is one very large caveat. The pesticides that the neonicotinoids replaced (organophosphates, pyrethroids, etc.) are what farmers will likely go back to if you get your way. Unlike neonics, those products were quite often responsible for large-scale bee kills. The systemics are safer because they are targeted to pests within the plant, rather than being sprayed indiscriminately over the field and drifting over the countryside. Where there have been isolated bee kills from neonics, they have been caused by planter dust due to the use of talcum powder to keep seeds from clumping together. This problem has been addressed and largely resolved.
    While it has been demonstrated that these insecticides can kill bees in a lab setting (they are, after all, insects), field testing is another story, and there are numerous beekeepers in corn and soybean country who see no trouble at all from these pesticides.
    As a beekeeper who just moved to a rural area, I’d be lying if I said I was not just a little nervous about the farmland surrounding me and what kinds of things these guys might be putting on their crops. Truth is, it would be nice to live in a world without pesticides. But unfortunately we do not live in a world without pests.

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  4. 4. berkeltree 11:52 am 03/20/2013

    Emacovik wrote “The systemics are safer because they are targeted to pests within the plant, rather than being sprayed indiscriminately over the field and drifting over the countryside.” This is exactly backwards. Neonicotinoids are less safe, because they go to all parts of the plant, including the flowers, and because they work at smaller than a part per billion. Honeybees gather pollen and nectar from the flowers; they also gather excess water exuded through leaves. They carry these substances back to the hive and feed the brood. This is not a matter of “isolated bee kills”, rather, it is likely the cause of colony collapse. Read the studies in Science.

    Link to this
  5. 5. emakovec 8:33 pm 03/20/2013

    I am familiar with the Science study about thiamethoxam
    being fed to bees, who were then driven various distances from home and tracked via RFID to see if they made it home. (Surprise, many of them did not.) It is unclear why they did not just put beehives into a crop treated with neonics and thus expose them to real-world doses.
    The fact is, these experiments are carried out all the time in the real world of agriculture. Just look at canola in Canada. This is a humongous crop, most of it both genetically modified and systemic-treated. It attracts hundreds of thousands of bee colonies for pollination, and accounts for the majority of the Canadian honey crop. Beekeepers would not be putting their colonies into those fields if they were coming home dead.
    When the CCD Working Group (made up of actual honeybee researchers) tested CCD deadout colonies for toxins, they found 46 different pesticides, and neonics were not high on the list. To quote Diana Cox-Foster, Ph.D., “Researchers here at Penn State don’t have any evidence to support that these neonicotinoids are the compounds that underlie CCD.”

    Link to this
  6. 6. bucketofsquid 5:22 pm 03/27/2013

    Last I read about CCD was that it seemed to be a combination of multiple factors including imported parasites.

    If these 3 pesticides are the main culprit then perhaps a more intelligent spraying policy would be better. The technology exists to pinpoint areas needing sprayed to within individual plants. Why not only hit the plants that need it and abandon crop dusting completely? Up front costs are higher but the long term payoff is far less chemical use and an abundance of bees for natural pollination.

    Link to this
  7. 7. emakovec 10:51 pm 03/27/2013

    Bucketsofsquid, what is different about these pesticides (a class known as neonicotinoids) is that they do not have to be sprayed. They are systemic, meaning seeds are treated with the material and it is present in the plant, where it kills the target pest that attempts to feed on the plant. To some people that is the scary part — if it kills the rootworms, won’t it also kill the bees that collect pollen a few weeks later? But in practice, the neonics have been far safer to bees (and to farmers) than previous pesticide types.

    Link to this

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