Impact of Pesticides on Pollinators

The science has become increasingly clear that pesticides, either acting individually or synergistically, play a critical role in the ongoing decline of honey bees and wild pollinators. Some pesticides produce sublethal effects in honeybees, which include disruptions in mobility, navigation, and feeding behavior. Decreased foraging activity, along with olfactory learning performance and decreased hive activity has also been observed. Other pollinators, such as the monarch butterfly, are indirectly affected by pesticides through habitat destruction brought on by the proliferation of genetically engineered (GE) crops and mono-crop agriculture. Part of the decline of monarch butterflies stems from the loss of milkweed, a native plant where the butterflies lay their eggs and is their main food source.

  • In 2015, researchers found that bumblebees exposed to field levels of neonicotinoids accumulate the toxic pesticides in their brains. Acute and chronic exposure increased neuronal vulnerability to mitochondrial dysfunction.
  • Another recent study provided supporting evidence to previous work showing that sublethal doses of imidicloprid, a toxic neonicotinoid insecticide, impairs olfactory learning in exposed honey bee workers. The study found that:
      • “Adults that ingested a single imidacloprid dose as low as 0.1 ng/bee had significantly reduced olfactory learning acquisition, which was 1.6-fold higher in control bees.”
      • “Bees exposed as larvae to a total dose of 0.24 ng/bee had significantly impaired olfactory learning when tested as adults; control bees exhibited up to 4.8-fold better short-term learning acquisition.”
  • In 2014, researches used Radio-Frequency Identification (RFID) tagging technology to examine how the day-to-day foraging patterns of bumblebees were affected when exposed to either a neonicotinoid (imidacloprid) and/or a
    Monarch Butterfly on Milkweed
    Monarch Butterfly on Milkweed. Photo by Lee Ruk. 
    pyrethroid (λ-cyhalothrin) independently and in combination over a four-week period. They found that neonicotinoid exposure has both acute and chronic effects on overall foraging activity; the performance of bees exposed to imidacloprid became worse, resulting in chronic behavioral impairment.
  • A recent study on monarchs attributed the disappearance of milkweed plants primarily to the use of GE corn and soybean crops. Scientists also point to the prolific use of herbicides in the Midwest eliminating these plants, and found that 70% of the losses of milkweed between 1995 and 2013 were located in agricultural areas.

For more details about the impact of pesticides on pollinators, see Beyond Pesticides’ BEE Protective page.

Economic Cost

In a 2009 study by Gallai et. al., the total economic value of pollinators globally was estimated to be $153 billion per year. Estimates vary for the United States as time moves forward, but regardless of the differing economic figures, the impacts of insecticides used on agriculture to bees and other pollinators are vast. In a 2005 study by David Pimentel, it was estimated that 5% of US honey bee colonies are killed due to pesticide exposure, leading to a $13.3 million annual loss. Honey and wax losses total to about $25.3 million a year. Pimentel speculated that due to the fact that 4-6 million hectares of land are heavily treated with pesticides, beekeepers cannot use what would otherwise be considered suitable apiary land. This yearly loss in potential honey production totals about $27 million. In addition to these losses, many crops fail due to lack of pollination. He estimated that these annual pollination losses caused by pesticides could be as high as $210 million. Pimental’s estimates are conservative, considering they were made before the advent of colony collapse disorder (CCD), and before large-scale pollinator losses began. In 2006, Losey and Vaughan estimated that native pollinators are responsible for $3.07 billion of fruit and vegetable production in the US. Then, in 2012, N.W. Calderone estimated that in 2009, the economic value of crops dependent on pollinators was approximately $15.12 billion for the US.

Litigation & Lawsuits

Beyond Pesticides, concerned citizens, and other environmental organizations filed a civil action suit against EPA in March 2013 for using clothianidin and thiamethoxam, two pesticides classified as neonicotinoids. The lawsuit aims to hold EPA accountable for the violation of Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the Endangered Species Act (ESA) and the Administrative Procedure Act (APA). EPA has approved the use of these pesticides without notification to the Federal Register, and without a public comment period, which violates FIFRA and the APA.

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Honeybees. Photo by Paul Rollings. 

In July 2013, several beekeeping organizations filed suit against the U.S. Environmental Protection Agency’s (EPA) to reverse a recent decision to register a new pesticide, sulfoxaflor, which is highly toxic to bees. This chemical is also considered by some scientists to be in the same class as neonicotinoids due to the fact that it has the same mode of action, although industry refuses to consider this claim, In December 2013, environmental and farm groups, including Beyond Pesticides, came together to file a legal brief in support of the nation’s major beekeeping associations’ lawsuit against the EPA. In March 2015, the 9th U.S. Circuit Court of Appeals agreed to hear the case.


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In March 2015, a federal court ruled against the use of neonicotinoid insecticides linked with destruction of bee colonies and other beneficial insects in national wildlife refuges in the Midwest region. The ruling capped a legal campaign to end the planting of genetically engineered (GE) crops and other industrial agricultural practices on national wildlife refuges across the country. In July 2014, FWS decided that it will phase out the use of GE crops to feed wildlife and ban neonicotinoid insecticides from all wildlife refuges nationwide by January 2016. This new policy still allows for case-by-case exceptions.

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What Can You Do?

A necessary first step is to avoid using toxic pesticides in and around your home, and encourage others to do the same. For other helpful tips, see Beyond Pesticides’ webpage on Managing Landscapes with Pollinators in Mind. Concerned residents can find more ways to take action in their community through the BEE Protective webpage.