16
Jul
Death of as Many as 107,000 Bumblebees from Neonicotinoid Insecticides Studied
(Beyond Pesticides, July 16, 2021) Recently published research reviews the 2013 Wilsonville, Oregon mass bumblebee die-off from application of the neonicotinoid dinotefuran on 55 linden trees in a big-box-store parking lot. In that single event, the research paper (published in Environmental Entomology) estimates between 45,830 and 107,470 bumblebees from some 289–596 colonies were killed. Reporting on the new study, by Entomology Today, quotes primary conclusions of the co-authors: “Our study underscores the lethal impact of the neonicotinoid pesticide dinotefuran on pollinating insect populations,” and, “It is likely that the vast majority of mass pesticide kills of beneficial insects across other environments go unnoticed and unreported.” As Beyond Pesticides has chronicled, the U.S. and the world are undergoing a pollinator crisis, caused in significant part by agricultural pesticides.
Dinotefuran, the neonicotinoid (neonic) that killed those Oregon bumblebees, is used against fleas, thrips, tree-boring caterpillars, emerald ash borers, hemlock woolly adelgids, and in the Oregon case, aphids. Entomology Today (ET) notes that the timing of this particular application could not have been worse: it happened on a warm day when the linden trees were in full flower and the bees out in force. Ironically, it occurred during Nation Pollinator Week. ET pens a sour footnote on the event: “The aphids posed no threat to the trees but rather to vehicles parked under them, which were spattered with the aphids’ honeydew waste.”
The authors write: “In addition to the effects that were documented in this study, there were several other documented pesticide poisonings that took place in Oregon in 2013 and affected bumble bee populations. These poisonings include applications of either imidacloprid or dinotefuran that resulted in lethal and sublethal concentrations . . . of these chemicals in the flowers of treated Tilia trees, up to seven months after the initial application. All dead bumble bees that were sampled had significant levels of imidacloprid or dinotefuran. Thus, the effects of neonicotinoids from applications to ornamental trees on non-target insects like bumble bees are likely widespread in the United States.”
Given what is known about the damaging impacts of neonics on bees and other pollinators, the study’s assertion of massive under-recognition of lethal neonic impacts is alarming. (See Beyond Pesticides reporting on neonics here, here, and here.) Although the agrochemical industry works hard to promote the idea that pathogens are responsible for the extensive bee and pollinator loss of the past two decades, ample evidence belies this whitewashing. Pointedly, the acute lethal impacts in the 2013 Wilsonville event and another a few days later in Hillsboro, Oregon contravene that contention in stark terms.
Emerging scientific consensus on central causes of bee loss focuses on pesticide impacts and how they make bees more vulnerable to pathogens. As Beyond Pesticides recently wrote, 2019 Canadian research “found that ‘real life’ exposures to neonicotinoid insecticides impair honey bees’ ability to groom harmful mites from their bodies, thus allowing mite populations to thrive.” In addition, Beyond Pesticides has discussed the coincidence, during the early 2000s, of the emergence of CCD [Colony Collapse Disorder] and severe colony losses with the spike in use of neonicotinoid pesticides, particularly delivered as seed coatings. In 2014, a study from the Harvard T.H. Chan School of Public Health showed that two neonics — imidacloprid and clothianidin — significantly harm honey bee colonies during winters.
Further, the damaging impacts of neonicotinoids are not confined to pollinators and their ecosystems. Declines in pollinator populations work their way up and down the food chain, from the plants that depend on pollination to the people that rely on the many foods that pollination provides. Beyond Pesticides wrote in June 2021, “Past research has found that the loss of pollination services would have a devastating impact on global nutritional health, with women and children most affected. . . . Many communities [already] lack access to healthy fruits and vegetables; allowing the pollinator crisis to continue unabated is likely to exacerbate these problems by increasing prices on important staples.”
At the time, the Wilsonville incident was the largest single mass bumblebee death event ever recorded. Mere weeks ago, Beyond Pesticides wrote about the second highest bee loss in 15 years, as documented in the Bee Informed Partnership’s 2020–2021 National Colony Loss and Management Survey. Populations of both wild and managed bees, as well as of other pollinators, have been devastated during the past two decades — much of that related to acute toxicity, as well as ongoing systemic but sublethal compromise of behaviors that sustain healthy hives and colonies.
The subject study, conducted by scientists from The Xerces Society for Invertebrate Conservation, The Ohio State University, the U.S. Department of Agriculture’s Agricultural Research Service, and the Oregon Department of Agriculture (ODA), asserts: “Insecticides, particularly systemic insecticides including neonicotinoids, are increasingly implicated in bee and other wildlife declines. The spectrum of effects on bees ranges from sublethal (i.e., not causing immediate mortality, rather behavioral and/or biological effects that reduce colony fecundity) to lethal depending on the dose and length of exposure.” (The Xerces Society originally reported the bumblebee deaths in Wilsonville to the Oregon Department of Agriculture.)
Dinotefuran is one of a large class of pesticides called neonicotinoids (neonics). Long-lasting and systemic compounds, they are absorbed into plant tissue and then distributed throughout the plant, making the pollen and nectar toxic to visiting pollinators. The researchers determined that some of the linden trees in the 2013 event were treated via aerial spraying, and some with a soil drench; their data analysis suggests that the soil drench method may actually have more-significant long-term effects on the plant tissues than the foliar method, but the authors acknowledge that these impacts are difficult to quantify.
They do note in their paper that other research has shown that “application of neonicotinoid insecticides on woody landscape plants at any time of year result in nectar residues that exceed concentrations shown to have negative effects on bees, even when label directions to protect pollinators are followed.” They also write, “Recent research suggests that there may be no safe time of year to apply systemic neonicotinoid insecticides to trees and shrubs to avoid sublethal/lethal effects on bees, even if label directions and bee precaution language are followed.”
According to ET, the linden tree flowers to which dinotefuran was applied in 2013 harbored very high concentrations of the insecticide. In their paper, the researchers note, “While most of the bumble bees that died in this mass killing were of a single, locally common species . . . that likely had the representation, resiliency, and redundancy to recover, there is no way of telling if colonies of rare or at-risk species of bumble bees were affected (we sampled less than 1% of all bumble bees killed). Given the scale and scope of this event, it is likely that if any colonies were nearby, that they may have been severely affected, potentially disrupting conservation and recovery efforts.”
That Wilsonville application violated dinotefuran’s label instructions, which indicate that the compound is toxic to bees that are exposed to it for more than 38 hours, and that the product is not to be applied to plants’ flowering parts, as was done in 2013. Subsequent to the Wilsonville and Hillsboro bee kills, the state temporarily banned use of the insecticide on plants, even by professional applicators, for 180 days, and indicated that ODA would conduct an investigation into the incidents, and then reassess the ban. In 2015, ODA moved to prohibit the use of pesticide products containing certain neonic active ingredients — dinotefuran, imidacloprid, thiamethoxam, and clothianidin — on linden (Tilia cordata), basswood (Tilia Americana), or other Tilia species trees in the state.
Many pesticides, including neonics, are infamous for their impacts on non-target species, as well as broad damage to ecosystems, habitats, and biodiversity. The study co-authors write, “The lethal effects of pesticide poisoning on non-target beneficial insects continue to occur today, as exemplified by the Wilsonville case, and is a contributor to pollinator decline. Furthermore, even sublethal effects of pesticides are likely interacting with other factors associated with bumble bee decline including habitat loss, climate change, and disease. Combined, these negative factors will likely continue to hinder efforts to recover and repopulate species identified to be at risk of population decline and extirpation.”
One might wonder, “Where is the U.S. Environmental Protection Agency (EPA) in this crisis of pesticide impacts on bees, other pollinators, and insects generally?” Historically, EPA has moved glacially on protections from this class of compounds. In January 2020, EPA did announce that it would review the registration of several neonics — acetamiprid, clothianidin, thiamethoxam, dinotefuran, and imidacloprid. At the same time, it announced interim decisions on some aspects of the uses of those five neonics. (See the agency’s web page titled “EPA Actions to Protect Pollinators.”)
The schedule for the registration review is introduced with this text: “The dockets for all the neonicotinoid pesticides have been opened. Our goal is to review the pesticides in this class in the same timeframe so we can ensure consistency across the class. As EPA completes risk assessments for the neonicotinoids, the Agency will pursue risk mitigation, as appropriate.” The public is encouraged to weigh in on the review of these pesticides, and is reminded of what Beyond Pesticides has repeatedly identified and called out: “the folly of the federal regulatory system’s attempts to ‘mitigate risks of pesticide exposure through small and piecemeal rules. ‘Mitigation’ of pesticide risks is a nibble around the edges of a pervasive poison problem.”
A recent Daily News Blog report said, “Despite [the agency’s] own acknowledgment of [the toxicity of neonics to bees and other pollinators], EPA has done little to curb their use. Indeed, in 2019, the EPA Office of the Inspector General (OIG) reported on the agency’s failure, saying that: “EPA has no means to evaluate the national impact of MP3s [state Managed Pollinator Protection Plans]; the agency has not developed a strategy to use data from a planned fall 2019 survey . . . to evaluate either the national impact of MP3s or the agency’s support of state MP3 implementation efforts; [and] EPA focuses primarily on acute risks (those that occur during a single exposure to a specific pesticide), and gives insufficient attention to chronic exposures to pesticides and to native pollinator protection activities.” Meanwhile, both Canada and the European Union have acted to rein in and ultimately, eliminate at least some neonicotinoids.
Neonicotinoids pose unacceptable threats to bees and other pollinators; their use should be eliminated not only because of those grave threats, but also, because they are not terribly good at their jobs. Ultimately, organic and sustainable farming practices can and should replace the chemical-intensive approaches that dominate agriculture in the U.S. because they eliminate pollinator (and all) toxicity issues, and foster greater resiliency to pests, to boot. That EPA continues to allow their use should be very concerning to everyone.
Learn more with Beyond Pesticides’ fact sheet, Managing Pests Safely Without Neonicotinoids, and its Bee Protective web pages. Beyond Pesticides offers guidance on avoiding use of neonicotinoid pesticides through its fact sheet, Managing Pests Safely Without Neonicotinoids, and its Bee Protective web pages.
Sources: https://entomologytoday.org/2021/07/08/new-study-revisits-2013-pesticide-bee-kill-wilsonville-oregon-dinotefuran/ and https://academic.oup.com/ee/advance-article/doi/10.1093/ee/nvab059/6305931
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
