(June 10, 2013, Beyond Pesticides) The Washington State Department of Agriculture (WSDA) on June 6 rejected a petition by Thurston County Commissioners to restrict sale, use and application of neonicotinoid insecticides. On April 8, 2013, the Commissioners requested the action by WSDA because of concerns about the effect of neonicotinoid insecticides on honey bee colony health. The Commissioners were acting on ‚Äúsubstantial bee colony loss in 2012‚ÄĚ reported by the Olympia Beekeepers Association. In its request, the Commissioners asked the state to implement a “restriction on the purchase, sale, distribution and application of the neonicotinoid class of insecticides for ornamental use to persons or entities with a valid WSDA pesticide applicator license” and indicated that “immediate action on a local level is appropriate and necessary.” Beyond Pesticides wrote a letter of support in favor of the petition.
Neonicotinoids are a relatively new class of insecticides that share a common mode of action that affect the central nervous system of insects, resulting in paralysis and death. They include imidacloprid, acetamiprid, clothianidin, dinotefuran, nithiazine, thiacloprid and thiamethoxam. According to the EPA, uncertainties have been identified since their initial registration regarding the potential environmental fate and effects of neonicotinoid pesticides, particularly as they relate to pollinators. Studies conducted in the late 1990s show that because these chemicals are systemic and are taken up by the vascular system of the plants neonicotinic residues accumulate in pollen and nectar of treated plants and represent a hazard to pollinators.
In rejecting the Thurston County request, WSDA director, Bud Hover, said, ‚ÄúWSDA shares your concerns about honey bee colony health and is acutely aware of the importance of honey bees and other pollinators to the economy and the environment of Washington. In 2011, the value of the crops pollinated by bees in Washington was in excess of $2.75 billion. Bees are also important for the pollination of fruit and vegetable gardens, as well as native plants. Certainly I am willing to take steps within my authority to protect pollinators when the evidence clearly shows that the neonicotinoid insecticides are a significant factor in their decline. I’m sure that you can understand and appreciate that I must consider the potential consequences of any rules that are adopted, and that I must make my decisions based upon sound science.‚ÄĚ
Sound science does not include, apparently, consideration of dozens of studies in the independent peer reviewed scientific literature that link neonicotinoid pesticides to bee health decline and colony collapse disorder (CCD). Instead, Mr. Hover said that the only thing that WSDA does know is that, ‚ÄúVarroa mites have a major negative impact on honey bee colony health.‚ÄĚ Advocates point to this lack of attention to the science in the name of ‚Äúsound science‚ÄĚ that represents a failure and state regulation of pesticides and ultimately puts beekeepers, farmers, and consumers at serious risk. If U.S. regulators evaluated the science as has been done by the European Union, advocates believe that there would be similar action to stop use of neonicotinoids.¬†Instead, state agriculture departments, like WSDA, and the U.S. Environmental Protection Agency have ¬†adopted policy that increases dependency on pesticides and genetically engineered plants that have hurt farmers because of insect and weed resistance and increasing pesticide reliance. Advocates are left to wonder who is being protected, the chemical companies or farmers, beekeepers, and consumers. And, they ask, at whose expense?
Acknowledging some reason for concern, WSDA wrote the Thurston County Commissioners the following:
1. Urge EPA in their reassessment of neonicotinoid insecticides (esp. the nitroguanidine subclass) to fully consider whether additional use restrictions are needed to protect bees when these products are applied to ornamental plant that are attractive to bees. Also, to make users more aware of potential risksfrom systemic uses, request that EPA require registrants to include advisory statements on neonicotinoid labels that have systemic uses (soil drench or tree injection) on ornamental plants that are ttractive to bees.
2. Independent of any required changes by EPA, request that registrants of neonicotinoid insecticides voluntarily add pollinator protection statements to theirlabels to address the potential risk of systemic uses on ornamental plants.
3. Request that WSU include presentations on pollinator protection in their pesticide licensing recertification courses, especially those courses that focus on urban and non-agricultural pesticide uses.
4. Provide technical assistance to all pesticide applicators who are licensed to apply insecticides to ornamental plants reminding them of their responsibility to protect pollinators.
5. Provide outreach to consumers by:
‚ÄĘ Assisting major retail trade organizations in creating point-of-sale brochures on pollinator protection that they can make available to their members to post at retail outlets.
‚ÄĘ Encouraging the news media to print timely articles on pollinator protection in their home and garden sections.
What the Science Shows
A. Neonicotinoids are toxic to bees
Neonicotinoids, like imidacloproid and clothianidin, have sublethal effects in honey bees, which include disruptions in mobility, navigation, and feeding behavior. Lethal and sublethal exposures have been shown to decrease foraging activity, along with olfactory learning performance and decreased hive activity. Bees living and foraging near agricultural fields are exposed as a result of multiple mechanisms throughout the spring and summer, and are exposed to foliar and systemic pesticides that studies are reporting cause feeding, navigation and learning behavior disruptions in bees. In fact, a 2013 study reports that sublethal doses of imidacloprid have cytotoxic effects on bee brains and that optic lobes are more sensitive to the insecticide than other regions of the brain of these insects. In a study looking at the acute effects of sublethal doses of clothianidin under field-like conditions at 0.05 -2 ng/bee, a significant reduction of foraging activity and longer foraging flights at doses of ‚Č•0.5 ng/bee during the first three hours after treatment were recorded. A study by Yang et al. reports that honey bees exposed to sublethal doses of imidacloprid show abnormalities in revisiting the feeding site, with some going missing. Returning bees also exhibit a delay in their return trips. A University of California (San Diego) study observed that sublethal doses of imidacloprid induce neurological effects (impaired waggle dancing at colony) that reduce communication and feeding. According to the researchers, waggle dancing can significantly increase colony food intake, and thus a sublethal dose of imidacloprid (0.21 ng bee‚Äď1) may impair colony fitness.
B. Neonicotinoid residues contaminate the entire plant
Neonicotinoids are systemic pesticides which mean that their residues are expressed in all parts of the plant, including leaves, pollen and nectar. A 2012 study by entomologist Christian Krupke, PhD, of Purdue University, clarifies some of the mechanisms by which honey bees are exposed to neonicotinoid pesticides. According to the study, in addition to agricultural sources, pesticide residues are found in pollen collected by bees and stored in the hive, in the soil of fields sampled, including unplanted fields, and in other flowering plants (dandelions). According to Dr. Krupke, clothianidin in/on the dandelions could have resulted from translocation from the soil to the flower, from surface contamination of the flowers from dust, or a combination of these two mechanisms. Guttated water of seed-treated plants, which provides a source of water for bees, can also be a source of contamination and exposure. Reetz et al. finds that corn seeds treated with clothianidin resulted in neonicotinoid concentrations up to 8,000 ng/ mL in the guttated fluid. Guttation drops from plants obtained from commercial seeds coated with thiamethoxam, clothianidin, imidacloprid and fipronil taken from young plants contained high levels of the neonicotinoid insecticides: up to 346 mg/L for imidacloprid, 102 mg/L for clothianidin, and 146 mg/L for thiamethoxam, according to a 2011 study. These residues remain and can expose foraging bees to significant levels of the insecticide.
C. Exposures to neonicotinoids leads to higher susceptibility to pathogens and parasites
Studies have also reported that bees exposed to sublethal does of pesticides are highly susceptible to pathogens that lead to their decline. One 2012 study by USDA researchers discovered that newly emerged bees exposed to sublethal levels of imidacloprid during larval development and indirectly from brood food from nurse bees had higher levels of the gut parasite Nosema spp. which is known to adversely affect colony health. According to the study, this suggests that being exposure to pesticides contributes to weakening bees by making them more susceptible to infection. Alaux, et al. reported that the combination of both imidacloprid and Nosema caused the highest individual mortality rates and energetic stress, suggesting a synergistic interaction between these agents and, in the long term, a higher susceptibility of the colony to pathogens. Similarly, Vidau, et al observed a significant increase in honeybee mortality when Nosema ceranae-infected honeybees were exposed to sublethal doses of insecticides.
D. Neonicotinoids also harm other beneficial organisms
Recent data also supports the harmful effects of neonicotinoids on other beneficial organisms. Imidacloprid residues in surface waters lead to a decline in macro-invertebrate abundance, according to a 2013 study. This study notes that short-term tests with the aquatic worm Lumbriculus variegatus, a high mortality was observed at the highest concentrations of imidacloprid in the sediments (1 to 5 mg/kg). At lower concentrations (0.05 to 0.5 mg/kg) effects were observed on growth and behavior of L. variegatus. In other tests with the aquatic invertebrates Chironomus tentans and Hyallella Azteca, chronic low-level exposure (>1.14 őľg l‚ąí1 for C. tentans) to imidacloprid reduced the species survival and growth. Imidacloprid has also been observed to be lethal to earthworms,16 with larger consequences for soil health and fertility.
Other bees such as bumble bees saw a significant reduction in growth rate and a reduction in the production of new queens when exposed to environmentally relevant levels of imidacloprid. One study observed that bumble bee micro-colonies exhibited a dose-dependent decline in fecundity, with a 33% reduction in brood production environmentally realistic dosages of imidacloprid.
For information on what you can do to protect the bees, go to Beyond Pesticides’ Bee Protective Campaign page.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.