Honeybee deaths linked to seed insecticide exposure


Honeybee populations have been in serious decline for years, and Purdue University scientists may have identified one of the factors that cause bee deaths around agricultural fields.

Analyses of 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 that those insecticides were present at high concentrations in waste talc that is exhausted from farm machinery during planting.

The insecticides clothianidin and thiamethoxam were also consistently found at low levels in soil - up to two years after treated seed was planted - on nearby dandelion flowers and in corn pollen gathered by the bees, according to the findings released in the journal this month.

"We know that these insecticides are highly toxic to bees; we found them in each sample of dead and dying bees," said Christian Krupke, associate professor of entomology and a co-author of the findings.

The United States is losing about one-third of its hives each year, according to Greg Hunt, a Purdue professor of , honeybee specialist and co-author of the findings. Hunt said no one factor is to blame, though scientists believe that others such as mites and insecticides are all working against the bees, which are important for pollinating and .

"It's like death by a thousand cuts for these bees," Hunt said.

Krupke and Hunt received reports that bee deaths in 2010 and 2011 were occurring at planting time in hives near . 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. Krupke said 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 said.

Krupke said 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 said.

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 said. "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 suggested that efforts could be made to limit or eliminate talc emissions during planting.

"That's the first target for corrective action," he said. "It stands out as being an enormous source of potential environmental contamination, not just for honeybees, 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. Krupke said protecting bees benefits agriculture since most fruit, nut and vegetable crop plants depend upon honeybees for pollination. The U.S. Department of Agriculture estimates the value of honeybees to commercial agriculture at $15 billion to $20 billion annually.

Hunt said he would continue to study the sublethal effects of neonicotinoids. He said for bees that do not die from the insecticide there could be other effects, 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," Hunt said.


Christian H. Krupke, Greg J. Hunt, Brian D. Eitzer, Gladys Andino, Krispn Given

Populations of honeybees and other pollinators have declined worldwide in recent years. A variety of stressors have been implicated as potential causes, including agricultural pesticides. Neonicotinoid , which are widely used and highly toxic to honeybees, have been found in previous analyses of honeybee pollen and comb material. However, the routes of exposure have remained largely undefined. We used LC/MS-MS to analyze samples of honeybees, pollen stored in the hive and several potential exposure routes associated with plantings of neonicotinoid treated maize. Our results demonstrate that bees are exposed to these compounds and several other agricultural pesticides in several ways throughout the foraging period. During spring, extremely high levels of clothianidin and thiamethoxam were found in planter exhaust material produced during the planting of treated maize seed. We also found neonicotinoids in the soil of each field we sampled, including unplanted fields. Plants visited by foraging bees (dandelions) growing near these fields were found to contain neonicotinoids as well. This indicates deposition of neonicotinoids on the flowers, uptake by the root system, or both. Dead bees collected near hive entrances during the spring sampling period were found to contain clothianidin as well, although whether exposure was oral (consuming pollen) or by contact (soil/planter dust) is unclear. We also detected the insecticide clothianidin in pollen collected by bees and stored in the hive. When maize plants in our field reached anthesis, maize pollen from treated seed was found to contain clothianidin and other pesticides; and honeybees in our study readily collected maize pollen. These findings clarify some of the mechanisms by which honeybees may be exposed to agricultural pesticides throughout the growing season. These results have implications for a wide range of large-scale annual cropping systems that utilize neonicotinoid seed treatments.

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User comments

Jan 12, 2012
Its in the soil for two years? But how long does a corn plant live? One year? So it's in the corn that I eat?

Jan 12, 2012
I'm sure the maker of this insecticide will fight this "accusation" to the death - even if scientifically proven to be fact (as it appears to be here). Money first - human and honeybee health at the bottom of the list. Containing the talcum powder exhaust and waste sounds like the first step though.

Jan 12, 2012
The one third of the bees in a year is going to lead to a 'Zeno's Paradox scenario. First year...2/3 of the bees still here....Second year (2/3)*(2/3)= 4/9 remaining bees of original population. You go ahead and construct your own Taylor Series and prove it to yourself. The formulae are in any calculus book.
So Tausch, the bees will never be completely gone, but the remainder may be naturally selected out of being willing to frequent corn fields, and that will kill the Greedy Obnoxious Pigs' (GOP) money machine, and the banks created contract conditions that forced them to use those nicotine based poisons. Hey, wonder how much of that stuff came from tobacco and the tobacco industry. That will involve the brit royal family too as they own all the tobacco companies thru their front company Brit Am Tobacco...BAT. So when corn production crashes..U NO HOO TOO BLAME....da BATty Queen and the GOP.

Jan 12, 2012
The bees are replaced each year with imported bees, many from Australia.

Jan 13, 2012
Pretty sure Europe has known this for years, and has had a ban in place on systemic insecticides?

From the wikipedia link on clothianidin:

"Seed treatment uses of clothianidin, corn in particular, have been revoked or suspended in Germany, Italy and Slovenia. The suspensions are reflective of E.U. pesticide law and are generally associated with acute poisoning of bees from pesticide dust being blown off of treated seeds, especially corn, and onto nearby farms where bees were performing pollinator services"

In germany a warning against using seeds with these insecticides was issued in 2004. In 2008 several types of seeds using it were banned (but this ban was partially revoked a few weeks later)

Jan 13, 2012
disgusting how they use so many pesticides and poisons in modern agriculture

Jan 13, 2012
@Tausch: Osiris is right on the math, but wordy.
First year 100%, and 33% die leaving 66. 1/3 of 67 dying is 22, leaving 45. 1/3 of 45 is 15, leaving 30. Then 20, 13, 9, 6, 4 3, 2.
And some new colonies are formed locally from hives with multiple queens, plus some are imported.

@Osiris1: Corn is wind-pollinated, not bee-pollinated, so corn yield won't be affected directly.

Jan 14, 2012
I'm sure the maker of this insecticide will fight this "accusation" to the death - even if scientifically proven to be fact (as it appears to be here). Money first - human and honeybee health at the bottom of the list. Containing the talcum powder exhaust and waste sounds like the first step though.

So...what...we'll go back to 18th century farming without pesticides and half the world will starve?

Jan 14, 2012
IMO these bees are dying of food allergy induced with GMO pollens, which are full of bacterial proteins. Bees have strong immune apparatus and their metabolism is trained to fight with every bacterial protein, which they can find in their food. The GMO contaminated pollens are spreading into will via cross-polination, so we have a global problem by now induced with Monsanto products and technologies. The white nose syndrome of bats is the problem of the same category, because the bats are well known pollen eaters. I'm explaining it here http://aetherwave...der.html .

Jan 14, 2012
@Modernmystic: - It would be better to move forward to smarter (with greatly reduced collateral damage) 21st century pesticides and have a surplus of food for 9 billion people.

Jan 14, 2012
@MM - Callippo shows an example of how biotechnology should be smarter. Corn borers do not eat pollen, so it does the corn (or farmers) no good for the corn to produce BT toxin in its pollen, yet it is the pollen from GM corn that does the most collateral damage to butterflies, bees, bats, birds, etc. Smarter GM corn would produce BT toxin only in the tissues that the corn borers eat. Even smarter GM corn would produce BT toxin in those tissues only when they start being eaten.

Jan 14, 2012
Perfect way to slim down population, kill the people with toxins in the food, they will never figure out it was their food.

Jan 15, 2012
So...what...we'll go back to 18th century farming without pesticides and half the world will starve?

And when the bees (and other insects) will be gone, what do you think will happen? It's not like we can hire people to replace what the bees are doing.

Jan 15, 2012
So MM - your "1" ratings means that you DON'T want smarter pesticides that let us feed 9 billion? And that you DON'T want smarter GM foods with reduced collateral damage?

I AGREE with you that going back to 18th century farming is not a viable option with our current population. We can't go back, and we can't even stay where we are. But we can make things better.

Jan 15, 2012
I like the idea of outsourcing the punishment of Monsanto top brass, et al., to the Chinese. When products over there cause harm due to corrupt officials, they make their point loud and clear- mainly loud.

Jan 21, 2012
If you truly do care and want to do something to help the bees, then plant echinacea and goldenrod on your property and along streams and canals. These plants help the bees to increase the vitality of their immune systems. Nature herself holds the key.

Jan 31, 2012
IMO the origin of CCD is the GMO pollen induced allergy. Bats are insensitive to imidacloprid but they consume the pollens, so they're dying too.
Note that nowhere in the paper do the authors argue that neonicotinoids are responsible for CCD.
The evidence from the paper is that imidacloprids induced increased susceptibility to pathogens in honeybees. That can also be said of environmental stressors such as poor diet and drought, as well as infection with Varroa mites.

The science is inconclusive on CCD, although most of the science points towards a combination of factors, as the paper from Mullin et al states.

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