A new study released by researchers at the Harvard School of Public Health (HSPH) blaming two neonicotinoid insecticides for being major causes of honey bee Colony Collapse Disorder (CCD) prompted Bayer CropScience to respond with high criticism of the research.

Lead author Chensheng (Alex) Lu, associate professor of environmental exposure biology at HSPH, said “We demonstrated again in this study that neonicotinoids are highly likely to be responsible for triggering CCD in honey bee hives that were healthy prior to the arrival of winter.”

Lu and colleagues who have assisted him in his research were inclined to blame insecticides for bee health problems prior to this study because they issued a study report with very similar results in 2012. This is their follow-up, which Bayer CropScience contends has as much or more bias against the insecticides.

Lu released the latest study through the Bulletin of Insectology on May 9.

Bayer scientists have reviewed the study and, in their opinion, “find it to be seriously flawed” for major reasons. The Bayer scientists listed their concerns in the three following bullet points:

  • “Feeding honey bees levels of neonicotinoids greater than 10 times what they would normally encounter is more than unrealistic—it is deceptive and represents a disservice to genuine scientific investigation related to honey bee health.
  • Given the artificially high levels tested over 13 consecutive weeks, the colony failure rates observed are completely expected.
  • Unfortunately, this latest study conducted by Dr. Lu repeats the fundamental flaws seen in his previous research and provides no meaningful information regarding honey bee risk assessment.”

Bayer also noted that the company “is committed to understanding the multi-causes that impact the health of pollinators by bringing together some of the brightest minds in agriculture and apiology to develop comprehensive solutions for bee health through its North American Bee Care Center which is part of the company’s $12 million investment in bee health in 2014.”

The Bee Care Center in the U.S. opened last month at the Research Triangle Park of North Carolina and has facilities for cooperative research with beekeepers, universities and others. Another major Bayer bee research center is in Europe.

Lu basically appears to have repeated much of the research done blaming for bee deaths and CCD in 2012; this time he included clothianidin, another neonicotinoid. He says neonicotinoids “appear to significantly harm honey bee colonies over the winter, particularly during colder winters.” He is saying that low doses of imidacloprid and clothianidin caused bees to abandon their hives over the winter and eventually die.

“Further, although other studies have suggested that CCD-related mortality in honey bee colonies may come from bees’ reduced resistance to mites or parasites as a result of exposure to pesticides, the new study found that bees in the hives exhibiting CCD had almost identical levels of pathogen infestation as a group of control hives, most of which survived the winter. This finding suggests that the neonicotinoids are causing some other kind of biological mechanism in bees that in turn leads to CCD,” according to the news release announcing the study results.

What the agriculture industry and Lu agrees on is that significant losses of honey bees cannot continue since bees are prime pollinators of roughly one-third of all crops worldwide. Experts have and are considering a number of possible causes, including pathogen infestation, beekeeping practices, and pesticide exposure.

Lu and his co-authors from the Worcester County Beekeepers Association studied the health of 18 bee colonies in three locations in central Massachusetts from October 2012 through April 2013. At each location, the researchers separated six colonies into three groups—one treated with imidacloprid, one with clothianidin, and one untreated. (As noted by Bayer, the amount of neonicotinoids feed the bees should have resulted in death and/or a CCD situation.) By April 2013, 6 out of 12 of the neonicotinoid-treated colonies were lost, with abandoned hives that are typical of CCD. Showing some of the diverse problems with honey bee mortality, one of the control colonies was lost—thousands of dead bees were found inside the hive—with what appeared to be symptoms of a common intestinal parasite called Nosema ceranae.

Lu referred back to the 2012 study in noting that mortality found in the 2012 study was even higher than the 2013 study results, and he suggested that the central Massachusetts winter of 2012, which was particularly cold and prolonged, has lead the research group to speculate that colder temperatures and the insecticide combination can play a role in the severity of CCD

Even though Lu claims to have demonstrated the validity of the association between neonicotinoids and CCD, he too sees the need for further research. Funding for the study came from Wells Fargo Foundation and the Breck Fund at the Harvard University Center for the Environment.