The Guardian (with a little help from Harvard) confirms what folks have suspected for a while – that Colony Collapse Disorder (CCD) is largely due to neonicotinoid pesticides:
In the new Harvard study, published in the Bulletin of Insectology, the scientists studied the health of 18 bee colonies in three locations in central Massachusetts from October 2012 till April 2013. At each location, two colonies were treated with realistic doses of imidacloprid, two with clothianidin, and two were untreated control hives.
“Bees from six of the 12 neonicotinoid-treated colonies had abandoned their hives and were eventually dead with symptoms resembling CCD,” the team wrote. “However, we observed a complete opposite phenomenon in the control colonies.” Only one control colony was lost, the result of infection by the parasitic fungus Nosema and in this case the dead bees remained in the hive.
Previously, scientists had suggested that neonicotinoids can lead to CCD by damaging the immune systems of bees, making them more vulnerable to parasites and disease. However, the new research undermines this theory by finding that all the colonies had near-identical levels of pathogen infestation.
“It is striking and perplexing to observe the empty neonicotinoid-treated colonies because honey bees normally do not abandon their hives during the winter,” the scientists wrote. “This observation may suggest the impairment of honey bee neurological functions, specifically memory, cognition, or behaviour, as the results from the chronic sub-lethal neonicotinoid exposure.” Earlier research showed neonicotinoid exposure can damage the renowned ability of bees to navigate home.
The new research follows similar previous work by the same group and comparison of the two studies shows that cold winters appear to exacerbate the effects of neonicotinoids on the bees.
Pesticides are necessary for modern high-yield agriculture, of course. But… so are bees.