What’s Killing The Bees?

A new study out of Harvard appears to strengthen the case that neonicotinoid pesticides are behind the sharp decline in the honeybee population over the past six years:

According to lead author Chensheng (Alex) Lu, “We demonstrated again in this study that neonicotinoids are highly likely to be responsible for triggering [Colony Collapse Disorder] in honey bee hives that were healthy prior to the arrival of winter.” To perform the latest study, the researchers examined 18 bee colonies in three different locations in central Massachusetts. They split each colony into three groups — one treated with a neonicotinoid called imidacloprid, one with a neonicotinoid called clothianidin, and one left in pristine condition to serve as a control group. The scientists monitored the groups from October 2012 to April 2013 and found that, by the end of that period, half of the neonicotinoid colonies had been decimated, while only one of the control colonies was destroyed by a common intestinal parasite, Nosema cerenae.

But Lisa Beyer points out that the study fed the bees dosages of insecticides “far in excess of anything bees would encounter in agricultural fields”:

In any case, it should be noted that whatever results the researchers created in the lab, in trials in which bees have been placed in farm fields treated with neonicotinoids, the colonies have done fine.

Lu’s new study nonetheless is receiving significant — and largely uncritical — media attention and strengthening the call by some environmentalists to prohibit neonicotinoid use in the U.S. Such a ban would be a mistake. It would compel U.S. farmers to use older pesticides that haven’t been subjected to bee studies and may be more hazardous to cultivated bees, not to mention wildlife and humans.

What’s more, the focus on neonics draws attention away from more plausible causes of bee deaths. First is the Varroa mite, which spreads lethal infections and has developed resistance to miticides. More research is needed on strategies to defeat this parasite. Second is the decline in bee food sources. High corn and soybean prices have accelerated the conversion of open land to cropland, leaving bees little to eat outside of the few weeks when a crop blossoms. Maybe if the government limited the subsidies that encourage fence-to-fence single-crop planting, more marginal land would be left fallow and could feed bees.

Bryan Walsh weighs both sides of the debate:

The chemical companies that make neonicotinoids are, unsurprisingly, skeptical that their products are behind the plight of the honeybee. “Extensive research has shown that these products do not represent a long-term threat to bee colonies,” David Fischer, the director of pollinator safety at Bayer, said in recent Congressional testimony. But the very purpose of pesticides is to kill insects, and no one would deny that such chemicals are almost certainly one of many factors hurting honeybees today. (It’s notable that a recent study found that the diversity of pollinators like bees was 50% higher on organic farms than on conventional farms.)

Many independent experts, however, doubt that neonicotinoids should get all the blame. Australia still uses neonicotinoid pesticides, but honeybee populations there are not in decline—something that may be due to the fact that varroahave yet to infest the country’s hives.

Recent Dish on the beepocalypse here and here.