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New Field Study Confirms Neonicotinoids Have Little Impact on Honeybees

As the Ontario provincial government in Canada considers policies that may force farmers to stop using, or drastically reduce use of, a class of pesticides called neonicotinoids, a new study shows why such policies are unlikely to do any good. Supposedly, limiting use of these pesticides will improve honeybee hive health, but such regulations will simply make it harder for farmers to produce an affordable food supply.

The study, which relies on data from actual field conditions, confirms that farmers can protect their crops using these chemicals without harming honeybee hives. Published in PeerJ, it assessed the impact of neonicotinoid-treated canola crops on hives that foraged among these crops in 2012. The researchers found no adverse impacts and very low exposure to the chemicals. The authors report:

Overall, colonies were vigorous during and after the exposure period, and we found no effects of exposure to clothianidin seed-treated canola on any endpoint measures. Bees foraged heavily on the test fields during peak bloom and residue analysis indicated that honey bees were exposed to low levels (0.5–2 ppb) of clothianidin in pollen. Low levels of clothianidin were detected in a few pollen samples collected toward the end of the bloom from control hives, illustrating the difficulty of conducting a perfectly controlled field study with free-ranging honey bees in agricultural landscapes. Overwintering success did not differ significantly between treatment and control hives, and was similar to overwintering colony loss rates reported for the winter of 2012–2013 for beekeepers in Ontario and Canada. Our results suggest that exposure to canola grown from seed treated with clothianidin poses low risk to honey bees.

Despite all the media hype about how these chemicals harm honeybees, these findings are not surprising.  Research condemning these chemicals has tended to focus on lab studies that overdose bees to see if pesticides affect hive health. But those studies have little relevance to real-life exposure to these chemicals in the field. The U.S. Agricultural Research Service’s Kim Kaplan explains that such studies have “relied on large, unrealistic doses and gave bees no other choice for pollen, and therefore did not reflect risk to honey bees under real world conditions.”

Over reliance on such studies creates a misleading impression about the risks to honeybees for many reasons. First, they ignore the fact that regular feeding or dosing of bees every day for a period of time is completely different than intermittent exposures from pollen in the field. As a result, even what some researchers claim are “field relevant” exposures are not really akin to real life exposures.

In fact, as this more recent study shows, when researchers study bees in real-life settings, they find no impacts from the chemicals and negligible levels of the chemicals in pollen, nectar and bee products, such as wax and honey. For example, Blacquière et al. summarize the research on such exposures in an article for Ecotoxicology published in 2012. The body of research, they explain, indicates that the exposures in pollen, nectar, and bee products are below levels that would pose acute or chronic toxicity. They also point out that, thus far, there are no field-relevant studies that demonstrate significant adverse impacts of neonicotinoids on honey bee hives. 

Last February, other researchers produced similar findings, as reported by Entomology today. These researches measured neonicotinoids in several crops grown from seeds treated with the chemicals. They could not find any traces of the chemicals on soybean flowers or cotton nectar. They found one neonicotinoid chemical in corn, but only in an insignificant amount. Dr. Gus Lorenz, a University of Arkansas who participated in this study concluded: “It’s not being expressed in the reproductive parts of the plants.”

So if public officials are looking to help honeybees survive better, they need to look elsewhere. Regulating neonicotinoids is unlikely to help and may force farmers to use other products that may pose greater risks to honeybees.