honey bees and insecticides
May 11, 2014

Two Common Types Of Insecticide Found To Harm Honey Bee Colonies

redOrbit Staff & Wire Reports - Your Universe Online

Imidacloprid and clothianidin, two widely used types of insecticides known as neonicotinoids, appear to cause significant harm to honey bee colonies during cold winter months, according to new research published Friday in the Bulletin of Insectology.

According to the study authors, who are affiliated with the Harvard School of Public Health, the findings reproduced a 2012 paper which found a link between low doses of imidacloprid and the phenomenon known as Colony Collapse Disorder (CCD), which causes bees to abandon their hives in the winter and die out.

However, the new study also found that clothianidin had a similar effect. In addition, while other research has hypothesized that CCD-related mortality in honey bee colonies could be the result of the insects’ reduced resistance to mites or parasites due to pesticide exposure, the new study has found otherwise.

In fact, the HSPH team found that bees in hives exhibiting CCD had nearly identical pathogen infestation levels as those found in control hives, the majority of which were able to make it through the cold weather – which suggests that the neonicotinoids are triggering a different type of biological mechanism that is responsible for CCD.

“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,” lead author Chensheng (Alex) Lu, an associate professor of environmental exposure biology at the university, explained in a statement.

CCD has caused a significant decline in the honey bee population over the past eight years, according to the researchers. Discovering the cause of this phenomenon will be essential to mitigating the problem, since the insects are responsible for pollinating nearly one-third of all global crops.

Over the years, many possible causes of CCD have been investigated, including pathogen infestation, beekeeping practices, and pesticide exposure. Recently, however, Lu and his colleagues have postulated that the phenomenon is specifically linked to neonicotinoids, which may impair the basic neurological functions of bees.

As part of their new study, Lu’s team analyzed the health of 18 bee colonies in three different locations throughout central Massachusetts between October 2012 and April 2013, said Damian Carrington of The Guardian. At each location, two colonies were treated with realistic doses of imidacloprid, two with clothianidin, and two others were not treated at all.

“Bees from six of the 12 neonicotinoid-treated colonies had abandoned their hives and were eventually dead with symptoms resembling CCD,” the team wrote, according to Carrington. The opposite phenomenon was observed in the control colonies – only one was lost, and that was due to infection by a common parasitic fungus known as Nosema ceranae. That colony had not been abandoned, as thousands of dead bees were found in the hives.

“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 concluded. “Hopefully we can reverse the continuing trend of honeybee loss.”