Pesticides and The Declining Honeybee

honey beeSilent Spring, by Rachel Carson, was instrumental in bringing about a nationwide ban on DDT and sparked the environmental movement that led to the creation of the U.S. Environmental Protection Agency (EPA). New science, however, has demonstrated that many of the claims made in Silent Spring were either exaggerated or wrong. Now, concerns about neonicotinoid pesticides (a.k.a. neonics) and declining honeybee populations are leading to bans and severe limitations on their use. Will banning “neonics” solve the problem? Just as careful research has indicated that DDT may not be as dangerous as once thought, careful research is revealing the truth about neonicotinoids.

Neonicotinoid Bans

In 2013, The European Union enacted a two-year ban on thiamethoxam, clothianidin, and imidacloprid as a result of fears that neonics might cause colony collapse disorder (CCD) among honeybees. In 2014, the EPA issued a moratorium on new or expanded use of neonics while it investigates the role of neonics in CCD. Recently, several major retailers (e.g. Lowe’s, BJ’s Wholesale Club, Home Depot) have decided to ban neonics as a result of pressure from the Friends of the Earth (FOE), which claims that “a meta-analysis of 1,121 peer-reviewed studies by the Task Force on Systemic Pesticides concluded neonicotinoids are a leading factor of bee declines and are harming birds, earthworms, butterflies and other wildlife”[1].

High concentrations of neonicotinoids have adverse effects on bees, but high concentrations are seldom reached in field applications. In fact, the concentrations used in most of the listed experiments are roughly 50 to 500 times higher than those found in the environment[2]. We actually know little about the effects on bees of low levels of neonics. Here is a summary of what is known.

  • Bees tolerate “field-relevant” doses of neonics without problem.
  • Bees don’t like the taste of neonics and avoid neonic-contaminated nectar.
  • Bees do bring neonic-contaminated pollen and dust to hives.
  • Bees fed high doses of imidacloprid over weeks/months do not necessarily succumb to CCD[3]-[5].
  • Despite increased use of neonics (3 million kilograms in 2012 [6]), honeybee populations in Europe and Australia are increasing and loss rates in the U.S. have decreased from ~33% per year to ~23%[7].
  • Varroa mites, which feed on bees, first began infesting beehives in California in 1993, closely approximating the rise of CCD[8].
  • Properly formulated neonics may help bees.
  • Regions with prominent CCD[9] are not necessarily regions with high neonic levels[10].
  • Making Decisions

    Imidacloprid is the most widely used insecticide in the world, primarily because it is less toxic to birds/mammals than organophosphate and carbamate insecticides. In fact, imidacloprid is so safe that it can be found in many anti-flea treatments. There is little evidence that neonics are the sole or even the primary cause of CCD. While increased study of neonics, development of alternative pesticides, and reduced pesticide use are all admirable goals, outright bans on highly valuable, relatively non-toxic pesticides are ill-conceived. Neonics are not ushering in a “second Silent Spring,” but rather are an important component of the arsenal that allows humanity to control the threats posed by increased globalization and the transport of pathogens around the world.


    [1] “Lowe’s commits to decisive action to protect bees and other pollinators,” Friends of the Earth. [Online]. Available: [Accessed: 15-Sep-2015].
    [2] “Neonicotinoids: Trying To Make Sense of the Science @ Scientific Beekeeping.” [Online]. Available: [Accessed: 15-Sep-2015].
    [3] J. S. Pettis, D. vanEngelsdorp, J. Johnson, and G. Dively, “Pesticide exposure in honey bees results in increased levels of the gut pathogen Nosema,” Naturwissenschaften, vol. 99, no. 2, pp. 153-158, Feb. 2012.
    [4] G. P. Dively, M. S. Embrey, A. Kamel, D. J. Hawthorne, and J. S. Pettis, “Assessment of Chronic Sublethal Effects of Imidacloprid on Honey Bee Colony Health,” PLoS ONE, vol. 10, no. 3, p. e0118748, Mar. 2015.
    [5] G. C. Cutler, C. D. Scott-Dupree, M. Sultan, A. D. McFarlane, and L. Brewer, “A large-scale field study examining effects of exposure to clothianidin seed-treated canola on honey bee colony health, development, and overwintering success,” PeerJ, vol. 2, p. e652, Oct. 2014.
    [6] “USGS NAWQA: The Pesticide National Synthesis Project.” [Online]. Available: [Accessed: 15-Sep-2015].
    [7] “ARS : Honey Bee Health and Colony Collapse Disorder.” [Online]. Available: [Accessed: 15-Sep-2015].
    [8] “Bee deaths and neonics: Inside story of Colony Collapse Disorder, Harvard’s Chensheng Lu’s crusade,” Genetic Literacy Project. .
    [9] “Honey Bee Disappearances: Could Pesticides Play A Role?” [Online]. Available: [Accessed: 15-Sep-2015].
    [10] B. Keim, “Bee-Killing Pesticides Found in Midwest Rivers,” WIRED, 04-Aug-2014. [Online]. Available: [Accessed: 15-Sep-2015].