Buzzkill: new studies link pesticide to bee population decline

beeSpring is in the air and with it typically comes the sound of buzzing bees floating through the air. Over the past few years, however, the usual buzz many are accustomed to has not been as prevalent as scientists continue to study a variety of factors, ranging from climate change to viruses to loss of habitat, that are contributing to the global decline of bees.

Now, two new studies recently published in the journal Nature are adding to evidence that overuse of neonicotinoid pesticides may also be contributing to the decline of bees. Also known as neonics for short, a recent article states they are among the most widely used insecticides in the world.

Coated onto corn, soy and canola seeds before they are planted, neonics are known for how simple they are to use. In fact, it’s estimated that treated seeds are used in more than 95% of the U.S. corn crop.

“The neonicotinoid [which is water soluble] is then absorbed as the plant grows … and protects the tissues,” explains scientist Nigel Raine in the article.

This is effective at protecting farmers’ crops from pests, but it may also be risky for the bees, because neonicotinoid residues appear in the nectar and pollen, even when the plant is flowering months later, Raine continued. This means when bees feed on the nectar of these flowering crops, they can be exposed to the pesticide.

As the name suggests, neonicotinoids, are derived from nicotine and act as a poison to the nervous system. According to the article, there has been a theory that bees might actually be repelled by it and avoid plants grown from these types of treated seed. However, one of the newly published studies suggests this is not the case.

Researchers in the United Kingdom conducted a lab experiment to see which kind of food sources bees are drawn to. They offered bees a choice between a plain, sugary solution and one laced with neonics. They found the bees preferred the pesticide solution.

“I think it’s a surprising result,” Raine said, “because the data suggest that they can’t taste the pesticides, but they still prefer them.”

The scientists from the study also noted it is possible that they’re getting a little buzz from the neonics, similar to the way a human may get a buzz from nicotine, which could be some sort of positive reinforcement meaning bees could be opting for the food source that may harm them.

In a second study, researcher Maj Rundlof and colleagues document the negative effects on the growth and reproduction of commercial bumblebee colonies feeding on flowering canola plants that were grown from seeds coated with neonicotinoids.

The study documents a negative effect on populations of wild bees — both in seed-treated fields and in adjacent meadows, but the study states the researchers did not observe a negative effect on honeybee colonies.

Scientists from one company that produce neonics wrote in a statement that the research “demonstrates yet again there is no effect of neonicotinoids on honeybee colonies in realistic field conditions, consistent with previous published field studies.”

However, given the accumulating body of evidence on the potential risk of neonics, there’s a growing movement to restrict their use. In fact, the European Union already has a temporary, partial ban in place restricting the use of some neonics, along with the Ontario government in Canada which has proposed a regulation aimed at reducing the number of acres planted with neonic-treated corn and soybean seed by 80% by 2017. In addition, the U.S. Environmental Protection Agency (EPA), announced earlier this month that it is unlikely to approve new neonicotinoid pesticide uses.

“I definitely think we are overusing neonicotinoids,” Christian Krupke, an associate professor in the department of entomology at Purdue University, said in the article. “We’re simply using too many of these compounds, in such an indiscriminate way,” he added.

Krupke also pointed to a recent EPA review that concluded using neonic-coated seeds offers little, if any, economic benefit to soybean farmers’ economic bottom lines. In other words, some farmers are using pesticide-treated seeds they don’t actually need.

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