The studied life of bees: Assessing the sting of neonic pesticides

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April 10, 2011 - 7:00pm

Beginning in the fall of 2006, some beekeepers began reporting losses of as much as 90 percent of their hives the bees simply disappeared.

That's a big concern because these vital insects pollinate as much as one-third of all the food we eat.

Some researchers suspect part of the problem is a relatively new class of pesticides called neonicotinoids (neonics) that we're using on food crops and in gardens and parks. Insecticides are meant to kill pests after all, but the key question is: Could residue in pollen and nectar be hurting bees?

To find out, Vera Krischik's entomology lab at the University of Minnesota is designing and running tests on bees.

"It's not an easy question to answer," Krischik said. "It was easy when you had a contact insecticide and you sprayed in on an insect and it died. The effect of poisoned food is just a complex issue."

One of the pesticides being tested is called clothianidin, which is used in treating everything from agriculture crops to trees to fruit and veggie crops. It was banned in Germany after a particular incident in 2008 where some clothianidin seed treatments didn't stick to the seed, and the pesticide dust killed a large number of bees. France and Italy have banned several other neonic pesticide treatments.

Clothianidin was registered "conditionally" with the Environmental Protection Agency in 2003. That means the agency approved its use but requested that the company conduct and submit follow-up studies. Lots of pesticides get registered this way.

"I would say the legislative preference is to get the product into the market if it doesn't hurt people and then if we find out it hurts the environment, we address that on the follow-up," said Brett Lorenzen, a lawyer and the Mississippi River Project Coordinator with the Environmental Working Group.

The EPA deals with more than a 100 pesticide applications a month. And the agency doesn't conduct its own research but relies on existing studies when reviewing an application.

With clothianidin, the EPA accepted a bee study that the maker Bayer submitted for its follow-up assessment.

"Controversy erupted over how study was done," Krischik said.

Basically, the researchers hired by Bayer set up different plots, some with poisoned plants and some with untreated plants. But Krischik said they let the bees roam in both plots.

"So then if you looked at the effects on bees, you had no idea what they foraged on. So that created the controversy that is this data that was out there, did it show anything, because the experimental design wasn't really getting at the question," she said.

Bayer didn't respond to requests for comment. But the EPA said it recently reclassified the Bayer study, moving it from acceptable to "supplemental," which means the agency doesn't really have data on the long-term effects of clothianidin on bees. In the meantime, the agency has required labels on the pesticide that forbid users from spraying it on crops when the plants are flowering.

"The issue here is that it's difficult to design a field study that we have confidence in will reflect what actually happens on field. You have to have a number of conditions like knowing where bees have foraged, what they foraged on," said Don Brady, of the EPA's scientific assessment department.

Krischik is working with the EPA to have her lab certified so that the research findings can be used in the EPA's review of clothianidin and other pesticides in this class.

So let's get back to the key question: Could pesticide residue in pollen and nectar be hurting bees?

Earlier studies tested nenoics by feeding bees tiny amounts of poison nectar. But that's not realistic, Krischik said.

"They're going to forage until they fill their gut up," she said. "They're going to be drinking more probably at a lower concentration because higher concentrations are not that often found in the field."

So Krischik's work at the University of Minnesota lab is taking a different approach.

On a recent afternoon, grad student Judy Wu has her dark hair pulled back into a looped ponytail, and she's put on bright purple medical gloves to administer different doses of sugar solution laced with pesticide.

"When you poison 30 or 40 bees at a time, and you start seeing them shake and die, it's really kind of sad. It's hard to watch," she said. But Wu said that she and her lab-mates remind themselves that it's worth sacrificing a few bees if it saves more in the end.

For the feeding, each bee is in one of those little plastic containers you put salsa in at a Mexican restaurant and Wu has poked a hole in the side to feed the bees. Using a pipette, she gives each bee a drop of the solution. Some of the bees get regular sugar solution, so she can tell if the results are really from the poison or just from being annoyed about being trapped in a salsa container.

Neonic pesticides work by mimicking natural insect neurotransmitters and then overwhelming its brain, leading to paralysis or death. But sometimes, in lower doses, it makes them writhe around or clean themselves fanatically.

After several minutes, some of the effects are starting to show.

"See that cleaning behavior Their hind legs stroke their abdomen, their front legs touch their face a lot. Now she's really getting into the grooming," Wu said.

In longer studies, in which the bees get poison doses for several weeks, sometimes "they do weird behaviors that you would never see in a bee. They start to lay eggs on each other, the bumblebees, or they start to make honey pots on each other, they start ripping up the substrate, making confetti and playing with it," Krischik said.

These kinds of behaviors may not kill a bee right away, but it means they can't collect food or find their way back to the nest or help build the colony.

That brings us to the trickiest part: Researchers can measure how the bees react to eating pesticide-tainted food in the lab, but how much poison are bees actually munching on in the wild?

That's why Krischik and her students are doing another experiment. They're growing plants in the greenhouse (and outside in the summer) and treating them with different neonics. Then they're gathering the pollen to measure just how much poison works its way into this bee food source.

With everything from seed treatments to spraying and irrigating, these neonic pesticides are definitely out in the environment. Lots of crop seeds are treated with neonic coating such as corn, soybeans, canola though this type of treatment is at fairly low concentrations. But then farmers and landscapers can also spray additional pesticide on leaves of the crop. One of the most concentrated treatments is sprays used on trees to prevent infestations such as the Emerald Ash Borer.

And, it's still not clear how long they linger, said Krischik, or if these pesticides are a key factor behind the disappearance of bees.

There's a lot riding on finding out. Bees are responsible for pollinating about $15 billion worth of crops. But pesticides are likely only one piece of the puzzle:

"It's not going to be one thing that is causing honeybee decline or causing bumblebee decline," Krischik said. "It's habit destruction, loss of food resources, poor quality food, loss of just the place to put your nest for a bumblebee, viruses, fungal diseases. We happen to be looking at pesticide issues, not to say other issues aren't as important.



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