Published: Thu 23 April 2015
I've blogged previously about
some of the alarmingly bad studies that have been done on pesticides and bees in recent years, so I'm happy to report that some folks have are doing solid work to address the flaws of earlier research. Unfortunately, the new results - at least when read at a very shallow level - seem to support what some of the crappy agenda-driven papers had tried to argue, so I'm sure those authors are now claiming vindication. But they haven't been vindicated. A broken clock isn't really right twice a day, it just looks that way if you're not paying close attention.
Let's move on to the new work, which consists of two papers in
Nature that are also nicely summarized in an accompanying piece. The fundamental question all of these papers are trying to address is whether a family of insecticides called News and Views neonicotinoids are deadly to bees. This is a critical issue, as bees are responsible for pollinating many of the crops that feed us, while neonicotinoids go a long way toward keeping those same crops from being devoured by insect pests. It doesn't help that organic agriculture fanatics have already decided to use the possibility of such a conflict as a rhetorical flourish in their crusade against The Evil Chemicals. Indeed, organic propagandists appear to have driven some of the poorly-designed experiments I've previously criticized, and have leaned on politicians to ban neonicotinoids in some areas. I don't like unnecessary chemical use, but it's just plain stupid to ban an important family of agricultural pesticides without a good reason.
If the results from the two new studies hold up, we might soon have a good reason.
Kessler et al. focused on seeing whether bees can taste neonicotinoid insecticides and thereby avoid ingesting them. That's been a major controversy, as much of the previous work on neonicotinoids has involved feeding bees nectar deliberately laced with pesticides, with the doses based on educated guesses about how much the insects would ingest in the field. If bees can taste and avoid the pesticides, though, then their actual field exposures would be far lower than what researchers were giving them in the lab, undermining those results.
Kessler's team decided to give the bees the
Pepsi challenge, offering honeybees ( Apis mellifera) or bumblebees ( Bombus terrestris) a choice between two feeders of sugar water, one laced with neonicotinoids and the other not. Neither species avoided the tainted food. In fact, two of the pesticides they tested actually seemed to make the sugar water taste better to the bees, leading them to drink more of it.
Rundlöf et al. tackled the other big question that's plagued many earlier studies: what really happens in the field? Even researchers who've set up beehives outdoors have usually relied on controlled feedings of neonicotinoids to measure the pesticides' effects, but farmers don't deliberately poison bees. In a working agricultural environment, the pesticides get sprayed on the crops at particular times to prevent or control specific pest problems. Whether any of those applications translate into bees ingesting the spray, and whether that has any effect, was largely a matter of speculation. Studying such a complex system in the field would, of course, be an enormous undertaking.
Rundlöf and colleagues were up for it. They analyzed sixteen fields of oilseed rape planted across southern Sweden. The seeds sown on eight of the fields had been treated with both a neonicotinoid insecticide and a fungicide, while the seeds on the other eight fields had only been treated with the fungicide. Once the crops were in, the investigators followed colonies of honeybees and bumblebees, and also tracked individuals of a solitary bee species,
Osmia bicornis. The bumblebees and solitary bees in the insecticide-treated fields fared significantly worse than those in the fungicide-only fields. Interestingly, the honeybees seemed to do about the same in both types of fields, undercutting earlier efforts to link neonicotinoids to honeybee colony collapse.
News and Views article by Raine and Gill concludes with an appropriate cautionary note:
Fundamentally, we must move towards finding the right balance between the risks of neonicotinoid exposure for insect pollinators and the value these pesticides provide to ensure crop yield and quality. Selective use of neonicotinoid seed treatments, on the basis of a demonstrable need for systemic pest protection, might help to reduce non-target exposure and slow the onset of pest resistance. We also need to consider and evaluate alternative options for pest control. It would be unfortunate if the recent focus on the risks from neonicotinoids led unintentionally to broader use of alternative pesticides that prove to be even more harmful to insect pollinators and the essential ecosystem services that they provide.
Good science, in other words, is leading us toward a much more nuanced view than our private agendas. It tends to do that.