bees and pesticides

In early June, Germany halted the sale of seven insecticides linked to the deaths of honeybees in 11,500 colonies. The main culprit was Bayer AG's corn seed treatment clothianidine (trade name Poncho), which the German crop research institute determined killed the bees. Bayer said improper seed handling caused particles containing the insecticide to blow away during the sowing of corn to nearby areas where it was ingested by the bees.

Last week, the ban was lifted for some of the products. Poncho is still on hold, but another product containing clothianidine (Elado) was given the green light, as were two based on the pesticide imidacloprid (Antarc and Chinook).

That these chemicals are fatal to bees is not a new discovery. I easily found a paper published in 2005 that found direct contact with clothianidine the most toxic of 6 insecticides tested; imidacloprid was found to be of intermediate toxicity.  In 2007, the French food safety agency AFSSA issued an "unfavorable opinion" on Poncho.

Previously, in 2004, France banned Bayer's Gaucho, another corn seed treatment containing imidacloprid (first banned by the country for use on sunflowers in 1999), because it was suspected of killing bees. Bayer denies this, and at least one study backed this up. However, Canadian beekeepers have the same conviction, and the study I read found toxicity with direct contact (such as must have occurred in Germany with Poncho), versus the study which found no harm using syrup infused with Gaucho in concentrations found in nectar.

Likewise, regulatory agencies are providing notification that residues of Poncho in pollen and nectar are below lethal levels. Nothing about direct contact. The EPA fact sheet (PDF) notes, however, that "Clothianidin is highly toxic to honey bees on an acute contact basis" and toxic to aquatic invertebrates. Not to mention ingestion of treated seeds being moderately toxic to small mammals, and a chronic toxic risk to small birds.

Treating corn seeds with these chemicals is arguably safer than spraying the stuff. And apparently the insects they combat are serious corn pests. Still, when bees and other pollinators are in such dire straits as it is, use of these chemicals seems like a risky proposition, particularly with the increased acreage being devoted to corn for ethanol. I'm not an agronomist, but which is worse: reduced corn crops due to insect infestation, or failure of many crops due to a loss in their pollinators?

[1] Ailey, J. B., et al. 2005. Contact and oral toxicity to honey bees (Apis mellifera) of agents registered for use for sweet corn insect control in Ontario, Canada. Apidologie 36: 623–633. (PDF)

Dead bee photo by Zoghol.

Thanks to Marty Lucas of the Big Eastern, one of my earliest followers, for providing me with the tip on the story.

Comments

[John]

I would prefer that the other crops get pollinated, but that's just me.

[Punk]

Let's see. They have Gaucho, the South American cowboy. Pancho, a Mexican revolutionary. How about El Diablo for the next pest/herbicide that annihilates every living, breathing organism?

[Rurality]

Every time I work the garden hotline, I get a call along the lines of, "I have a problem with ____ (insect) on my ____ (vegetable). I've been putting Sevin on it, will that help?" I always make a point to ask them if they realize that Sevin is toxic to bees. So far I haven't talked with anyone who knew that.