The Pesticide Connection
This scientific study, undertaken by Dr. Richard Gill and colleagues at the University of London and featured recently in Nature magazine, indicates that two pesticides may be the cause of colony collapse disorder. In the words of Gill and team, "chronic exposure...to two pesticides...impairs natural foraging behavior and increases worker mortality."
While previous studies examined the impact of pesticides on the individual physiology of bees, Gill's study focused on overall hive behavior and survival as related to the pesticides neonicotinoid and pyrethroid. While these pesticides may have subtle effects at the individual level, their combined impact on bee hive survival, whether through shared metabolic processes or reduced hive communication ability, was shown to be lethal.
The Experiment and Its Results
To simulate exposure to neonicotinoid and pyrethoid pesticides, Gill and team exposed entire colonies of 40 bumblebees each to these pesticides at levels approximating those in and around fields. The result was nothing short of alarming. The average number of bees lost as a result of the pesticide exposure, whether dead in the hive nesting box or dead due to failure to return to the hive, was about two thirds of the total against a third of the total for a control group. In the experiment, the pesticides caused a 100 percent increase in bee mortality.