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It's been about a decade since scientists began documenting a die-off of bees. Bees are critical to the food supply since they pollinate billions of dollars of crops each year from almonds to citrus to blueberries. As scientists have tried to get to the bottom of the bees' plight, one theory that has emerged is that a class of pesticides known as neonicotinoids may be part of the problem. NPR's Allison Aubrey reports on two papers published today in the journal Nature. They offer more evidence that these pesticides are contributing to bees' decline.
ALLISON AUBREY, BYLINE: Over the last 10 years, neonics, as they're called for short, have become ubiquitous. They're used on millions of acres of corn, soybeans and canola. The reason - they're very easy to use. As scientist Nigel Raine of the University of Guelph explains it, there's no spraying. All farmers have to do is buy seeds that are already coated with the pesticide. They're known as pretreated seed.
NIGEL RAINE: That's the idea. So you drill it into the ground, and the neonicotinoid is then absorbed as the plant grows, and the active ingredient goes up into the plant and protects the tissues.
AUBREY: Now, this can fend off pests, which is good for farmers' crops, but it may be bad news for bees...
RAINE: ...Because you get neonicotinoid residues in the nectar and pollen even when the plant is flowering some months later potentially.
AUBREY: And this means when bees come to feed on the nectar of these flowering crops, they can be exposed to the pesticide. Now, neonics, as the name suggests, are derived from nicotine and act as a poison to the nervous system. And there's been a theory that bees might actually be repelled by it and avoid plants grown from treated seed. But one of the new studies published today suggests this is not the case. Researchers in the U.K. conducted a lab experiment to see which kind of food sources bees are drawn to. The offered bees a choice between a plain, sugary solution and one laced with neonics. And they found that bees seemed to prefer the pesticide solution.
RAINE: I think it is a surprising result because the data suggest that they can't actually taste them but they are still preferring them...
AUBREY: They might be getting a little buzz from the neonics similar to the way a human might get a buzz from nicotine?
RAINE: I think it might be a similar sort of pathway, yes - that they're getting some sort of positive reinforcement.
AUBREY: And the upshot is that bees could be attracted to the very food source that may harm them. Now the extent to which neonics do impact bee health is controversial because the results of studies have been mixed and there are many factors from climate change to habitat loss that are contributing to bee decline. One of the companies that produces neonic pesticides, Bayer, maintains that the amount of pesticide that bees are typically exposed to are OK. Here's Bayer's Becky Langer.
BECKY LANGER: Our studies find that when pesticides are used according to label, there's no long-term colony health effects.
AUBREY: But the second study published today challenges this thinking. Researchers in Sweden document negative effects on the growth and reproduction of commercial bumblebee colonies feeding on flowering neonic-treated canola fields. They also document a negative effect on populations of wild bees, both in treated fields and in adjacent meadows, though they did not observe a negative effect on honeybee colonies. Given the accumulating body of evidence on neonics, some countries are imposing restrictions. The EU has a partial ban in place, and in Canada, there are proposals to cut back the use of pretreated seeds. Christian Krupke is a professor in the Department of Entomology at Purdue University and has studied the issue.
CHRISTIAN KRUPKE: We're just simply using too many of these compounds. We're using them in such an indiscriminate way.
AUBREY: And he points to a recent EPA review that found there's little if any economic benefit to soybean farmers' bottom lines from using them. In other words, some farmers are using pretreated seeds they don't need, and in doing so, may be risking the long-term health of bees. Allison Aubrey, NPR News.
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