Yes, Insecticides Kill Bees. Studies ID Chemical That May Contribute to Colony Collapse

By Sarah Zhang | March 29, 2012 2:54 pm

spacing is important
Honey bees tagged with RFID chips

The mysterious drop in honey bee populations—often called colony collapse disorder for lack of a more specific name—has generated a long list of suspects that includes mites, viruses, malnutrition, and even cell phone radiation. Two new studies published in Science suggest that neonicotinoids, a class of widely used insecticides, may belong at the top of the list.

That an insecticide kills insects like bees is not particularly surprising. Neonicotoinoids have already been partially banned in Italy, Germany, and France for their possible role in colony collapse disorder. Still, it remains one of the most common pesticides: one neonicotoinid alone, imidacloprid, is authorized for use on over 140 crops in 120 countries. Results from the two new studies suggest that even doses that do not kill the bee immediately can have enough ill effect to eventually cause colony collapse.

The first study in the UK compared 75 bumble bee colonies that researchers had exposed to varying levels of neonicotoinoids over 14 days. (Colony collapse disorder refers specifically to honey bees, but bumble bee numbers have been dropping off too.) After six weeks of foraging in the field, the colonies exposed to low and high levels of insecticide were 8% and 12% smaller, respectively, than controls. They also produced on average only one or two queens compared to nearly 14 in unexposed colonies. Since bumble bees die off every winter and only the queen survives to found a new colony in the spring, it’s easy to see how this could spell bad news for bumble bee populations.

A second team in France, previously profiled in Discover, tracked the movements of individual honey bees. They were tagged with RFID chips (tiny chips—see picture above) that alerted researchers each time a bee got back to the hive safely. When the researchers released these bees out randomly in the wild, only 56.8% of exposed bees made it back compared to 83.1% of unexposed ones—a difference that is enough to tip colonies to collapse, according to population models. The exposed bees may have been too disoriented to navigate, as neonicotoinoids kill by messing with receptors in the brains of insects.

Results from these two studies point toward a role of neonicotoinoids in colony collapse, though ultimately, there are probably multiple interconnected reasons. For example, previous research has found that neonicotoinoids also make bees more susceptible to fungal pathogens. Despite the work of pesticide companies trying to find alternative explanations, it’s looking increasingly likely that their chemicals have some role in killing bees.

Image: Science / AAAS

CATEGORIZED UNDER: Environment, Living World
  • Tandem

    I would be willing to bet that while the doses they are exposed to don’t outright kill them, their concentration of such chemicals in their food supply (and ours) chiefly honey, sets them up for a concentrated dose of the pesticides that eventually affects their growth, reproduction, navigation, and overall health.

  • Linda George

    Does anyone know what these chemicals do to humans once they enter the food chain?

  • Peter Snow

    I have had bees for years and the last 10 years my hives have lost bees regularly. Currently I don’t have any bees and even when a new swarm comes they may last for a season or sometimes two but eventually the hive will be empty, not even dead bees in the hive and the honey is robbed by nonresident bees. I don’t have any idea what happens but the bees just fly away and don’t ever come back.

  • Corey

    Linda, they act like very very low doses of nicotine. So, not much. That’s why we use them over organophosphates and other nasties. But, as discussed, their affect on arthropods is orders of magnitude worse.

  • Barb Hoffmann

    So will the US wait till all the bees are gone before these insecticides are banned?

  • Iain

    From wikipedia
    Studies conducted on rats suggest that the neonicotinoids may adversely affect human health, especially the developing brain.
    Neonicotinoid seed treatment uses are banned in Italy, but foliar uses are allowed. This action was taken based on preliminary monitoring studies showing that bee losses were correlated with the application of seeds treated with these compounds; Italy also based its decision on the known acute toxicity of these compounds to pollinators

  • JD

    I am wondering if the problem could come from genetically modified crops that cause resistance from insects. I know bees love to gather pollen from corn and if this contains pesticides it is not good for bees.

  • previoushoosier

    when i lived in indiana i learned that it takes 9 lbs of pesticide to grow one pound of corn. when will this insanity stop? each of us can make a difference. apply yourself to action.

  • Bonny

    I have personally experienced a bee hive behind the chimney in the wall of my house. I am convinced that bees take off with an extra queen in the spring and settle where ever they can. If it is in someone’s house then they are destroyed. The bees I had were very docile. I could run the lawnmower right by the hive and they just ignored me. I tried in vain to get bee keepers to come and get them, even advertising online. When they crawled around the chimney into the house I had to get rid of them and had them exterminated. I hated doing it but no one would come and get them. I think that is the fate of most of the bees. Exterminators are doing their job all to well.

  • Mike

    Watch the movie Vanishing of the Bees. It explains why bees are not returning to their nests. Mostly because they are poisoned from the pesticides.

  • Kaviani

    Bayer Co. is responsible for the greatest push of imidacloprid domestically. You know who to avoid…

  • Brian

    previoushoosier Says:
    “when i lived in indiana i learned that it takes 9 lbs of pesticide to grow one pound of corn. when will this insanity stop? each of us can make a difference. apply yourself to action.”

    Seems a bit suspicious given that, by weight, pesticides are more expensive than corn. A little critical thinking goes a long way… like pesticides.


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


80beats is DISCOVER's news aggregator, weaving together the choicest tidbits from the best articles covering the day's most compelling topics.

See More

Collapse bottom bar