Lu, Warchol, and Callahan sketched out a plan. In the spring of 2010, they would set up 20 hives at four locations, two in Uxbridge and two in Northbridge. They would feed all the hives high fructose corn syrup, mimicking a common commercial beekeeping practice. (Beekeepers typically supplement their colonies’ food supply with syrup or sugar.) In four of the five hives at each site, the syrup would contain imidacloprid, a commonly used neonicotinoid. The fifth hive, the control in the experiment, would be fed syrup not dosed with pesticide.
They began with a population of roughly 220,000 bees that grew into 1.4 million or so. On July 1, 2010, they started the pesticide regimen, beginning with very low doses, to make sure they didn’t kill the bees right away. They upped the amounts after four weeks to levels that Lu says were on the conservative end of what bees encounter in the real world — through syrup made from corn treated with neonicotinoids or nectar and pollen collected from contaminated flowers and crops. The four pesticide-laced hives at every site were given different concentrations of imidacloprid.
Winter came, and they saw nothing. The hives seemed fine. “We were starting to get discouraged,” Warchol says. “Dick and I were talking, saying, ‘Wow, there’s really nothing going on.’ ” Lu had the same reaction. “At that time,” he says, “I thought my hypothesis was wrong.”
Then everything started to change. Around the beginning of 2011, a beekeeper whose yard they were using as a testing site reported seeing a mass of bees suddenly fleeing one of the hives. It was suicide — to endure the winter, honeybees typically cluster together inside their hive for warmth, surviving on food that a beekeeper has provided to sustain them. Some of the bees had dropped dead on the surrounding snow. The rest had disappeared.
Over the next several weeks, Lu, Warchol, and Callahan lost 15 of the 16 hives they had fed imidacloprid. It resembled colony collapse disorder, with abandoned hives bearing plenty of food. “It was an exciting moment in a sense, even though the bees were dying,” Warchol says. For Lu, it all clicked. “It’s not Mother Nature,” he says. “It’s us.” They lost one of their control hives to disease, but it looked very different from the hives the bees had fled, with dead bees littering the colony.
When Lu, Warchol, and Callahan sought to publish their results, they encountered resistance. Some journals wouldn’t take the manuscript. Peer reviewers raised objections. They finally published in 2012 in an Italian journal called the Bulletin of Insectology. They also wrote a letter alerting the US Environmental Protection Agency to their work, just as two European research teams announced similar findings.
Critics challenged their science, the design of their experiment, and their conclusions. One California beekeeper was especially strident, going to great lengths to try to discredit their study. A leading bee researcher called it “an embarrassment.”
Others, like May Berenbaum, head of the Department of Entomology at the University of Illinois at Urbana-Champaign, offer more measured criticism. Berenbaum questions Lu’s sample size, saying sweeping conclusions are impossible from 20 hives. She also cites a separate study that found no evidence of neonicotinoids in commercially available high fructose corn syrup, which she says undermines the premise of bees being exposed to pesticides through the food provided by beekeepers. (Lu dismisses these objections, saying 20 hives was plenty, statistically speaking, and that no historical record exists on neonicotinoid levels in corn syrup.)
A self-described “tree-hugger,” Berenbaum is highly critical of systemic pesticides. She just hasn’t seen enough evidence to support banning them. If and when it reaches that point, she says, “I’d be the first one in line” pushing to restrict their use. “It’s a seductively easy fix,” she says, noting that many other chemical residues have been found in dead bees. “But like many seductively easy fixes, it is, I think, not likely to fix everything, or maybe even fix enough.”
For Lu, the push-back to their study — and the fact that no one, to his knowledge, sought to replicate it — emboldened him to go back into the field. “He’s a very passionate guy,” Callahan says. “There’s no question about it.”
So Lu, Warchol, and Callahan established new testing hives at three sites in 2012. They varied their methods somewhat, in part by testing bees’ exposure to both imidacloprid and another neonicotinoid called clothianidin. The results, they say, only reinforced their conclusion that pesticides are likely a major culprit behind colony collapse.Continued...