In a new study from Harvard University, scientists linked a massive honeybee die-off to two specific types of widely used insecticides.
According to the Guardian, two classes of insecticides known as neonicotinoids killed about half the colonies in the study. Conversely, none of the colonies treated with nothing at all saw any bees die.
Study lead author Chensheng Lu, an expert on environmental exposure biology at Harvard School of Public Health, and his team published their work in the journal Bulletin of Insectology.
"We demonstrated that neonicotinoids are highly likely to be responsible for triggering 'colony collapse disorder' in honeybee hives that were healthy prior to the arrival of winter," he told the Guardian.
From Oct. 2012 to April 2013, the researchers analyzed 18 bee colonies in three areas in Central Massachusetts. At each location two colonies were given reasonable doses of imidacloprid, two received clothianidin and two were untreated to act as control hives. In only one untreated hive, the bees died, but it was due to a parasitic fungus, not the insecticide.
"Bees from six of the 12 neonicotinoid-treated colonies had abandoned their hives and were eventually dead with symptoms resembling CCD," the scientists wrote in the study. "However, we observed a complete opposite phenomenon in the control colonies."
While other colonies began to increase starting in Jan. the pesticide-treated colonies continued the decline most hives experience in the winter. In total, the 12 pesticide-treated colonies had a 50 percent mortality rate. In a study conducted a year earlier, the scientists noted the mortality rate was 94 percent, but that was in a prolonged winter.
"Although we have demonstrated the validity of the association between neonicotinoids and CCD in this study, future research could help elucidate the biological mechanism that is responsible for linking sub-lethal neonicotinoid exposures to CCD," Lu said in a press release. "Hopefully we can reverse the continuing trend of honey bee loss."
