New Study Finds Combination of Pesticides Dangerous To Bumblebees

Bumblebee pollinating. Photo by Kabir Bakie/Wikimedia.

A recent study from the School of Biological Sciences, Royal Holloway, University of London found harmful affects on bumblebees from a combination of pesticide exposure of two pesticides-neonicotinoids and pyrethroids. The study, which evaluated these pesticides concentrations in conditions that could approximate field-level exposure, found that chronic exposure to these insecticides:

impairs natural foraging behaviour and increases worker mortality leading to significant reductions in brood development and colony success. We found that worker foraging performance, particularly pollen collecting efficiency, was significantly reduced with observed knock-on effects for forager recruitment, worker losses and overall worker productivity.

The researchers, Richard J. Gill, Oscar Ramos-Rodriguez and Nigel E. Raine, also found that combined “exposure to pesticides increases the propensity of colonies to fail.”

The University of London’s study is part of a growing body of evidence that implicates neonicotinoids in the decline of the world’s bee population.

Popularity of Neonicotinoids

Worldwide, neonicotinoids are the most widely used class of insecticides.  In 2008, for example, such pesticides were registered in 120 countries and had a global market share of 1.5 billion euros (roughly about $2 billion U.S. dollars) – 25% of the world insecticide market.

As a class, neonicotinoids include insecticides such as clothianidin, imidacloprid, thiamethoxam, among others. The insecticides work by paralyzing insects: they block “specific chemical pathway that transmits nerve impulses in the insect’s central nervous system.” Systemic pesticides have become popular because they are considered to be more effective in insects than in the nervous systems of mammals.

Neonicotinoids are systemic insecticides because the chemical is absorbed and spreads throughout the plant. According to the Xerces Society, a non-profit organization that seeks to protect wildlife through the conservation of invertebrates and their habitat, “[p]lants absorb these chemicals through their roots or leaves, and the vascular tissues transport the chemical into stems, leaves, flowers, and even fruit.”

In the United States, a citizen petition filed by environmental groups and 25 individuals last year asked the EPA to suspend the registration of clothianidin, manufactured by Bayer A.G. as well as other companies, because of the imminent hazard to bees, described neonicotinoids as follows:

While used on dozens of crops, the predominant use of neonicotinoids is as a seed treatment for corn. Production of corn for food, feed and ethanol production is the largest single use of arable land in North America, occurring in nearly every State and reportedly reaching a near-record 92 million acres in 2011 (a cumulative area virtually equivalent to the entire country of Germany); it is expected to continue to climb. Almost all of the corn seed planted in North America, except for 0.2% used in organic production, reportedly is coated with neonicotinoids, primarily clothianidin and its closely related compound, thiamethoxam.

Despite the concern raised by the Citizen Petition, the EPA declined to suspend the registration the systemic pesticide stating, among other things, that there is no “evidence adequate to demonstrate an imminent and substantial likelihood of serious harm occurring to bees and other pollinators from the use of clothianidin.”

As an aside, in the United States, not only is most of the corn treated with neonicotinoids, it is also predominantly genetically engineered.  According to statistics released last July by the U.S. Department of Agriculture, 85 percent of all corn planted was genetically engineered.

EPA’s Reaction to UK Study

The EPA did not specifically comment on the newly released study from the U.K. but the agency is reviewing neonicotinoid pesticides as a group during its mandatory 15 year registration review. According to information on the EPA website, the agency has moved the review of several of these pesticides ahead in the schedule. It has also cautiously mentioned that “[s]ome uncertainties have been identified since their initial registration regarding these pesticides’ potential environmental fate and effects, especially as they relate to pollinators.”

Earlier this year, three studies further advanced the already strong connection between neonicotinoids and the bee die offs that have become the new norm for many North American beekeepers. In light of this growing evidence, the EPA’s inaction, as seen by critics, is a reflection of the EPA’s pro-corporation slant.

In the past several years, France, Germany, Italy and Slovenia have banned or suspended the use of some neonicotinoids.

Beekeepers Concerned 

The agency’s response has beekeepers worried. Steve Ellis, for example, told the Star Tribune recently that he lost 500 hives during this summer.

Tom Theobald, a Colorado beekeeper and activist who has seen the impact of neonicotinoids firsthand, told GMO Journal that he is disappointed in the response from the U.S. regulators. He is concerned that the heavy reliance on neonicotiniods is a “huge environmental disaster” in part because these systemic pesticides have a propensity to remain in the soil for long periods of time and accumulate over years thus creating an environment that is hostile to bees. Mr. Theobald believes that the EPA has not used “sensible judgment” in reviewing the science on systemic pesticides.