High insecticide levels in dead honey bees

PURDUE (US) — Honey bee populations have been in serious decline for years, and scientists may have identified one of the factors that cause bee deaths around agricultural fields.

Analyses of bees found dead in and around hives from several apiaries over two years in Indiana showed the presence of neonicotinoid insecticides, which are commonly used to coat corn and soybean seeds before planting.

The research showed those insecticides were present at high concentrations in waste talc that is exhausted from farm machinery during planting, according to findings published in the journal PLOS ONE.

“We know that these insecticides are highly toxic to bees; we found them in each sample of dead and dying bees,” says co-author Christian Krupke, associate professor of entomology at Purdue University.

The United States is losing about one-third of its honey bee hives each year, says Greg Hunt, professor of behavioral genetics, honey bee specialist, and co-author of the findings. No one factor is to blame, though scientists believe that mites and insecticides are working together against the bees, which are important for pollinating food crops and wild plants.

“It’s like death by a thousand cuts for these bees,” Hunt says.

Bee deaths in 2010 and 2011 were occurring at planting time in hives near agricultural fields and toxicological screenings performed by Brian Eitzer, a co-author of the study from the Connecticut Agricultural Experiment Station, for an array of pesticides showed that the neonicotinoids used to treat corn and soybean seed were present in each sample of affected bees.

Other bees at those hives exhibited tremors, uncoordinated movement and convulsions, all signs of insecticide poisoning.

Seeds of most annual crops are coated in neonicotinoid insecticides for protection after planting. All corn seed and about half of all soybean seed is treated. The coatings are sticky, and in order to keep seeds flowing freely in the vacuum systems used in planters, they are mixed with talc. Excess talc used in the process is released during planting and routine planter cleaning procedures.

“Given the rates of corn planting and talc usage, we are blowing large amounts of contaminated talc into the environment. The dust is quite light and appears to be quite mobile,” Krupke says.

The corn pollen that bees were bringing back to hives later in the year tested positive for neonicotinoids at levels roughly below 100 parts per billion. “That’s enough to kill bees if sufficient amounts are consumed, but it is not acutely toxic,” he says.

On the other hand, the exhausted talc showed extremely high levels of the insecticides—up to about 700,000 times the lethal contact dose for a bee.

“Whatever was on the seed was being exhausted into the environment,” Krupke says. “This material is so concentrated that even small amounts landing on flowering plants around a field can kill foragers or be transported to the hive in contaminated pollen. This might be why we found these insecticides in pollen that the bees had collected and brought back to their hives.”

Krupke suggests efforts could be made to limit or eliminate talc emissions during planting.

“That’s the first target for corrective action,” he says. “It stands out as being an enormous source of potential environmental contamination, not just for honey bees, but for any insects living in or near these fields. The fact that these compounds can persist for months or years means that plants growing in these soils can take up these compounds in leaf tissue or pollen.”

Although corn and soybean production does not require insect pollinators that is not the case for most plants that provide food. Protecting bees benefits agriculture since most fruit, nut, and vegetable crop plants depend upon honey bees for pollination.

The U.S. Department of Agriculture estimates the value of honey bees to commercial agriculture at $15 billion to $20 billion annually.

Hunt says he plans to continue to study the sublethal effects of neonicotinoids. Even bees that don’t die may be affected in other ways, such as loss of homing ability or less resistance to disease or mites. “I think we need to stop and try to understand the risks associated with these insecticides.”

The North American Pollinator Protection Campaign and the USDA’s Agriculture and Food Research Initiative funded the research.

More news from Purdue University: http://www.purdue.edu/newsroom/

chat8 Comments


  1. E Hill

    Why talc, don’t people know talc is manufactured from asbestos?!?!?!?

  2. Christian

    Answer: Beekeepers should refuse to loan/hire their bees to GMO/modified and pesticide altered crops. It isn’t rocket science…if someone wanted to borrow my car but I knew they were intending on destroying it for their own person gain and convenience I probably wouldn’t loan it to them…same thing with the bees. Beekeepers shouldn’t serve farmers who use these pesticides (or really any pesticides) on their crops…and this problem would be solved in a few years, irresponsible farmers would be forced to either find another way to pollinate or act socially responsible and stop poisoning the environment. Why should beekeepers be FORCED to watch their livelihood be crushed and die, just for the sake of Monsanto’s profit margin and a farmers ‘convenience’?

  3. Ben

    *sarcastic comment in 3..2..1..* Huh, insecticides are kill bees? Wow.. who would have thought that bees would be killed by that stuff?

  4. R.T.Whitson III

    Talc used to be made from soapstone, and I don’t know anything about the geology or current mining/production processes, as the comment about asbestos refers to. However, no matter what substance might be used (for instance corn starch, a very effective and safe, powdered lubricant which ought to yield similar results), as long as the product was still mechanically aerosolized and distributed in the wind, it would still spread the insecticides, and THEY are the real problem, NOT the substance used to keep the grain flowing.
    The answer is to find ways to avoid the use of toxins to keep the crops safe from insects.
    Has anyone investigated the use of capsicum (the hot chili component) on an industrial quantity level? It has long been preferred by home gardeners as an effective, safe, and organic alternative to chemical insecticides. I know folks that simply put their own home-grown habeneros in a blender with water, and spray that on their garden plants. They swear by it. Would that be toxic to bees?

  5. Robert Reed

    Hot Chili spray is toxic to Bees and Wasps….no simple answer if we are to continue industrial agriculture in the way we do.
    I liked the cornstarch idea but what a mess in the rain. I like the thought of no insecticide whatsoever but how do you limit insect damage to industrial crops?
    There is not an easy silver bullet answer to Bee decline and mortality in North America.
    It is obviously driven by a number of things both “natural” and human caused.
    I liked the comment about Beekeepers demanding that Farmers certify insecticide free fields before placing hives, though.
    It needs to go so much further, from safe havens for Bees and hives, to clean soil and water for forage and food crops…the list is long, and would dramatically alter the rural industrial landscape of the USA if slowly but surely but we could wean ourselves off industrial agricultural chemicals….mostly. But what would our food supply look like!?
    Until that day, enjoy your tumors, everyone!

  6. Elizabeth


    Bees will forage up to six miles away from their colonies so avoiding exposure is a challenge for anyone who lives in corn country.

    Also, the neonicotinoid pesticides are widely used by homeowners, municipalities, golf courses, nurseries and so on . . . Exposure is virtually inescapable if you keep your bees within a few miles any of these things.

  7. Alex

    insecticides are bad for animal health … really ?

  8. Julie

    As soon as I saw this, I thought of the documentary “Vanishing of the Bees”. Even then, honeybee farmers thought that insecticides were responsible for the sudden death of many hives. The culprit was a change in the formula.. how have we effectively been keeping insect levels down without effecting the crops all the years before 2008+?

    The bottom line is, honeybees are so important to our food chain. If the insecticides are killing them, it’s time to rethink our strategy. So many bees have died off at this point that it would be a better idea to use none at all until populations regenerate.

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