New Evidence Linking Systemic Pesticides To Bee Die Offs

Honey bee approaching a flower.  Photo from

Honey bee approaching a flower. Photo from

Four new studies demonstratively link systemic pesticides to colony collapse disorder (CCD), a phenomenon where bees fail to return to their hives leading to massive decline in bee colonies. This new information effectively puts to rest denials about the impact of systemic pesticides on pollinators.

In the United States, neonicotinoids, a systemic class of pesticides, “coat a massive 142 million acres of corn, wheat, soy and cotton seeds. They are also a common ingredient in home gardening products.” These pesticides are of a particular concern because they kill sucking and chewing insects by disrupting their nervous system. Furthermore, “unlike older pesticides that evaporate or disperse shortly after application, neonicotinoids are systemic poisons. Applied to the soil or doused on seeds, neonicotinoid insecticides incorporate themselves into the plant’s tissues, turning the plant itself into a tiny poison factory emitting toxin from its roots, leaves, stems, pollen, and nectar.” And they persist in the soil for longer than the older generation pesticides.

Two studies published on March 29, 2012 in Science document that a “widely used insecticide can threaten the health of bumblebee colonies and interfere with the homing abilities of honeybees.”

In the one study, a research team at the University of Sterling, U.K., exposed bumble bees to field-realistic levels of the neonicotinoid imidacloprid, a clothianidin predecessor, then allowed them to develop naturally under field conditions. The researches found that “[t]reated colonies had a significantly reduced growth rate and suffered an 85% reduction in production of new queens compared to control colonies.” They concluded that the “impacts of imidacloprid on reproduction of wild bumble bee colonies are likely to be widespread and significant, particularly as this chemical is registered for use on over 140 crops in over 120 countries” and suggested that there “is an urgent need to develop alternatives to the widespread use of neonicotinoid pesticides on flowering crops wherever possible.” (See Neonicotinoid Pesticide Reduces Bumble Bee Colony Growth and Queen Production, Penelope R. Whitehorn, Stephanie O’Connor,Felix L. Wackers, Dave Goulson, Science, Vol. 335 No. 6076, March 30, 2012).

In the second study, Mickaël Henry and his team at the French National Institute for Agricultural Research in Avignon, France, tagged free-ranging honeybees with RFID, or, radio-frequency identification microchips, and gave some of the bees a sublethal dose of thiamethoxam, another common systemic pesticide used on cotton, cherries, strawberries, and tomatoes. The research team found that the “treated bees were about two to three times more likely to die while away from their nests.” It is believed that the bees died because the pesticides interfered with the bees’ ability to navigate their way back home. When the researchers took the data and plugged it into a computer simulation model the results showed that bee populations could suffer “a marked decline in a matter of weeks,” which leaves the bees “more susceptible to other stresses such as parasites and climate change.” (See A Common Pesticide Decreases Foraging Success and Survival in Honey Bees, Mickaël Henry, Maxime Beguin, Fabrice Requier, Orianne Rollin, Jean-François Odoux, Pierrick Aupinel, Jean Aptel, Sylvie Tchamitchian, Axel Decourtye, Vol. 335 No. 6076, March 30, 2012.)

In a Harvard University study, which will be published in the June issue of the Bulletin of Insectology, the researchers observed four different bee yards each containing four hives treated with different levels of imidacloprid and one control hive. They discovered that “after 23 weeks, 15 out of 16 of the imidacloprid-treated hives—94%—had died. Those exposed to the highest levels of the pesticide died first.” The research team leader Chensheng (Alex) Lu, associate professor of environmental exposure biology in the Department of Environmental Health, commented that “[s]trikingly, it took only low levels of imidacloprid to cause hive collapse—less than what is typically used in crops or in areas where bees forage.”

Similarly, a study released in January by Purdue University Professor Krupke’s research team, shows two separate pathways in which neoniconitinoids contribute to the decline in bees: “an acute one during spring corn planting, when huge clouds of neonic-infested dust rises up, at doses that kill bees that come into contact with it. Those population losses weaken hives but don’t typically destroy them. And then there’s a gradual effect—what scientists call ‘chronic’—when bees bring in pollen contaminated at low levels by neonicotinoids.” (See Multiple Routes of Pesticide Exposure for Honey Bees Living Near Agricultural Fields, Christian H. Krupke, Greg J. Hunt, Brian D. Eitzer, Gladys Andino, Krispn Given.)

The research confirms what many beekeepers have long suspected. Colony collapses in the magnitude of 30-90% began to be reported in the U.S. shortly after the Environmental Protection Agency (EPA) conditionally approved Bayer AG’s systemic pesticide, clothianidin, in 2003 for treatment on corn and canola seeds. Such losses are approximately double the normal expected winter decrease. Pointing to evidence linking systemic pesticides to bee die offs that existed before, during and after Bayer AG applied for registration of clothianidin, many argue that the EPA failed to protect the nation’s pollinators by permitting the sale and marketing of this systemic pesticide.

Growing tired of sitting on the sidelines and watching their livelihoods disappear, 25 beekeepers, together with honey producers and four environmental and consumer groups, recently filed an emergency citizen petition with the EPA, urging that the agency take action on clothianidin. Represented by Center for Food Safety, the petitioners cited many failures by the EPA in permitting the sale and marketing of clothianidin. They argued that the agency “dropped the ball and consistently underestimated the extent of translocation and the levels of exposure to clothianidin and other neonicotinoids that honey bees and other beneficial insects are suffering.”

The petitioners also stated that “[i]t is long past time for the agency to stop giving these pesticides a free pass.” The burden of proving that clothianidin meets the EPA’s criteria to be entitled to continued registration, they argued, rests with Bayer AG, which the company failed to meet for nine years. The petitioners further argued that in the face of mounting evidence and the European experience with clothianidin’s predecessor, imidacloprid, the agency should have acted more rigorously to protect bees and other insects but, instead, the agency:

loosened its oversight, allowing farmers to inundate fields with toxic chemicals  before EPA has confirmed their safety. In particular, the agency continues to maintain the registration status for clothianidin despite the fact that  the registrant, Bayer AG,  has failed to conduct a required study satisfying EPA’s standards after having more than nine years to gather the needed data. EPA has definitively stated that Bayer’s belated attempt to conduct a field study of clothianidin’s effects on pollinators did not satisfy the condition on registration. Yet, the agency has never identified any alternative study that supports a finding that clothianidin does not have any unreasonable adverse effects on the environment—including pollinators. Such a finding was, and remains, a prerequisite to conditional registration. Continuing to allow clothianidin to be marketed, sold and used when not one study meets EPA’s condition for its registration is, as a matter of law, arbitrary, capricious and contrary to the mandates of FIFRA [Federal Insecticide, Fungicide, and Rodenticide Act] and the APA [Administrative Procedure Act].

Underscoring the agency’s lack of oversight on this issue, the petitioners argued that “this is not a situation in which new evidence casts doubt on EPA’s prior findings about the environmental hazards of clothianidin,” although there is plenty of that, rather, “the essential step EPA imposes for conditional registration has never been completed.” (emphasis in the original). The petitioners asked that the agency respond to the petition within 90 days and suspend registration of clothianidin and issue a stop sale order or, alternatively, suspend clothianidin’s conditional registration.

One of the petitioners, Tom Theobald, a Colorado beekeeper for over three decades and the founder of Boulder County Beekeepers’ Association, expressed a concern to me that after nine years of continued use of systemic pesticides, it may be a little too late, stating that “GMOs and systemic pesticides are the opening acts in an ecological disaster of monumental proportions.” Furthermore, “[e]ven if steps are taken now to rein in the systemic pesticides, which seems unlikely, it may already be too late for American beekeeping.”