Why Bees Probably Can’t Avoid Pesticides Even if They Wanted To

Pesticides such as as neonicotinoids are already under close scrutiny because research appears to show that, certainly for honey bees at least, they may interrupt the insect’s normal behaviors and they are suspected to play a part in colony collapse disorder.

One of the ways in which the pesticide industry has fought back against those claims is to point out that such studies have always involved much higher doses of neonicotinoid exposure than would occur in the wild, saying that the bees would flit between crops and flowers, some of which will have the pesticides, some of which won’t, and that even if they were negatively affected, the bees would learn to avoid particularly problematic areas.

Two separate studies published this month in the journal Nature appear to show that pesticides may have an affect not just on honeybees but other wild bees, while a second study shows that bees may have developed a preference for nicotine-like pesticides.

The first study was conducted by researchers at Lund University in Sweden. To counter claims by pesticide companies that the artificial set-up of experiments has affected past results, they attempted to create a real world experiment where they analyzed the activity of bees in eight fields of oilseed rape sown with seeds treated with the insecticide clothianidin per the manufacturer’s instructions, and eight fields that were not treated.

The researchers found that bumblebee hives stopped growing, meaning the number of bees was less than those in the untreated fields, and they produced less queens who would then go on to set up their own colonies. That said, the honeybees, which are our chief pollinators for crops, did not appear to be affected, but researcher Maj Rundlöf told Nature in a separate report that the honeybees may not be more resilient, it could just be the fact of their greater numbers. The study her team conducted could only account for a population reduction greater than 20 percent in overall colony size, so it might be that the honeybee die-off was shielded by their greater numbers but that they still suffered a potentially significant change.

This may help to clarify a long-standing issue with bee studies. Scientists had supposed that honeybees would be reflective of the general population, but that might not be true. Also, this might be why bee studies into insecticide exposure have shown mixed results when counting overall population numbers. Further investigation into these issues will be needed to determine if that is the case, but it certainly is a cause for interest.

The second study released in Nature this past week was conducted by researchers from Newcastle University in the UK, and specifically looked at whether, as pesticide makers have claimed, bees will avoid plants that have been treated with harmful pesticides.

To do this the researchers confined a sample of honeybees and a sample of bumblebees to separate boxes and then provided them with nectar that was unaltered and nectar that had been laced with one of three insecticides: imidacloprid, thiamethoxam or clothianidin.

The bees did not appear to show a preference for the unaltered nectar and instead showed a significant preference for the nectar samples containing imidacloprid or thiamethoxam. Pesticide companies have claimed that the bees’ behavior could have been modified by the experiment as it wasn’t a natural setting and, in the interests of strict scientific rigor this is something the researchers also acknowledge, but the preference appears to be quite marked and this certainly is a blow to companies that defend pesticides by saying the bees will simply avoid that which is not good for them.

In a further blow to that argument, the researchers also analyzed how the bees taste neurons react to different concentrations of neonicotinoids. They found that the bees can’t taste the neonicotinoids at any concentration, and so they couldn’t avoid it if they wanted to. As to why the bees prefer insecticides, we don’t yet fully understand the cause but the researchers have suggested that neonicotinoids may interfere with the bees’ normal brain activity to generate what is essentially the beginnings of an addiction to the insecticide-laced nectar, something that has been shown in rat studies.

Neonicotinoids are currently banned in Europe despite individual governments like the UK saying that there is not enough evidence to suggest that pesticides harm our pollinators. While this research won’t convince skeptics–indeed, the pesticide industry has reportedly brushed these studies off as being flawed–many researchers seem to agree that insecticides are changing bee behavior, and increasingly with harmful effects.

Photo credit: Thinkstock.

59 comments

Mark Donner
Mark Donner1 years ago

Bill Arthur criticizes people who object to chemicals decimating their health and the future of the planet as "chemophobics". According to him, you must implicitly trust the anything from the billionaire crooks who have made money for decades from genocide and ecocide. Who are you working for, Bill Arthur

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Sarah Hill
Sarah Hill2 years ago

I have seen more bees this year than I have for a while!

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Siyus Copetallus
Siyus Copetallus2 years ago

Thank you for sharing.

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Julia Oleynik
Julia Oleynik2 years ago

Thank you for sharing

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Philip Wilkins
Philip Wilkins2 years ago

Just read the article that Bill A suggested.
I cannot believe it has been published - just effectively says everything is fine, these chemicals are incredibly safe without any real evidence to back it up. Then says bees are increasing in Europe - hsa the author been to Europe? Bees are NOT increasing. Even people without any interest in nature are noticing there are distinctly fewer bees year on year.
This may not be neonicotinoids, but it leads me to disbelieve the whole article. It tries to claim that it is disproving a theory by using science then presents no real evidence.

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Paulinha Russell
Paulinha Russell2 years ago

Thanks

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Danuta Watola
Danuta Watola2 years ago

thank you for sharing

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Nikki Davey
Nikki Davey2 years ago

Thanks

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Karen and Ed O.
Karen and Ed O2 years ago

I have to make a correction to the comment I made on the 28th. I said that Bayer makes Premarin. Now I don't know where that came from but it is made by Wyeth Pharmaceuticals which is part of Pfizer.
Me Culpa.

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Mahmoud Khalil
Mahmoud Khalil2 years ago

thanks

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