(Beyond Pesticides, October 8, 2025) A study, Pesticides detected in two urban areas have implications for local butterfly conservation, published in partnership with researchers at Xerces Society for Invertebrate Conservation, University of Binghamton (New York), and University of Nevada, reports widespread pesticide residues in the host plants of butterflies located in green spaces in the cities of Sacramento, California, and Albuquerque, New Mexico. Just 22 of the hundreds of collected samples had no detectable residues, with all other samples containing some combination of 47 compounds of the 94 tested pesticides in the plant tissue. Of the 47 compounds, 4 are neonicotinoid insecticides linked to adverse effects for bee and pollinator populations based on previous peer-reviewed research. The fungicide azoxystrobin and the insecticide chlorantraniliprole were detected at lethal/sublethal concentrations, according to the report authors. “Residential landscapes have high conservation potential for butterflies and other invertebrates,” says Aaron Anderson, co-lead author of the report and pesticide program specialist at Xerces Society for Invertebrate Conservation. He continues: “But, these findings show how pervasive pesticide contamination can be in towns and cities, and underscore that protecting wildlife in these areas includes addressing pesticides.” The report’s results underscore the pervasiveness of pesticide drift and dispel the myth […]

(Beyond Pesticides, October 2, 2025) This year marks an advancement of various state-level neonicotinoid laws and regulations, including in Maine, Vermont, and Connecticut—emphasizing surging public support for pesticide reforms. The Maine legislature passed, and Governor Janet Mills (D-ME) signed into law on July 22, 2025, LD 1323, which commissions the Board of Pesticide Control to study the impacts of neonicotinoids and neonicotinoid-treated seeds, which advocates hope will help advance future legislation to prohibit the use, distribution, and sale of neonicotinoid insecticide products. Meanwhile, after years of grassroots advocacy, the Connecticut legislature advanced, and Governor Ned Lamont (D-CT) signed SB 9 into law, which will partially restrict the nonagricultural use of neonicotinoids on turfgrass, starting in 2027. There was a more comprehensive effort that failed to move forward (HB 6916), which would have gone further by restricting or prohibiting the use of neonicotinoids on trees, shrubs, and treated seeds (see here for Beyond Pesticides comments). Maine and Connecticut join eleven other states (California, Nevada, New Jersey, Massachusetts, Maryland, Minnesota, New York, and Vermont) in taking steps to restrict or prohibit the use of neonicotinoids. (See Daily News here.) Whether it is a campaign to ban glyphosate, paraquat, chlorpyrifos, atrazine, or any […]

(Beyond Pesticides, September 29, 2025) With the theme “Our Home Outdoors,” the National Environmental Education Foundation (NEEF) launched National Public Lands Day this past Saturday—defining this year’s event as follows: “Our public lands are more than just places to visit—they are woven into the fabric of our everyday lives. From the trails we hike to the parks where we gather with family and friends, these spaces are our collective backyard, our shared front porch, our natural playground.” At the same time, people are asking their local governments whether they are using petrochemical pesticides and fertilizers on their parks and playing fields that are known to threaten the health of children, pets, wildlife, and the environment. Beyond Pesticides led a nationwide action to “Tell your local officials to make your parks organic.”  For those engaging with their local elected officials and parks departments, Beyond Pesticides, through its Parks for a Sustainable Future program, offers technical support to transition parks to organic land management through analysis of soil health, development of a plan to improve soil biology to cycle nutrients for healthy plants, training of staff to implement the organic plan, and ongoing consultation for plan adjustments when necessary. Organic systems focus […]

(Beyond Pesticides, September 26, 2025) National Public Lands Day on Saturday, September 27—first established in 1994 and held on the fourth Saturday of September—is organized by the National Environmental Education Foundation (NEEF) in partnership with the U.S. National Park Service and participating federal agencies. Events are planned at neighborhood, state, and national parks nationwide, and entrance to National Parks will be free for the day. Coinciding with National Organic Month, this year’s theme, ”Our Home Outdoors,” is explained by NEEF as: “Our public lands are more than just places to visit—they are woven into the fabric of our everyday lives. From the trails we hike to the parks where we gather with family and friends, these spaces are our collective backyard, our shared front porch, our natural playground.” Beyond Pesticides began its work on organic land management in national parks nearly a decade ago at National Historic Sites in Arkansas, Kansas, and Iowa. The program, now the Parks for a Sustainable Future program, partners with local communities in pursuit of a future where (1) public lands, from parks to playing fields, are managed without toxic pesticides, (2) children and pets are safe to run around on the grass, and (3) […]

(Beyond Pesticides, September 24, 2025) A novel study of chronic toxicity of the neonicotinoid insecticide thiamethoxam to honey bees (Apis mellifera), published in Insects, finds sublethal effects that threaten the survival of bee larvae and the health of bee colonies. “We evaluated the effects of thiamethoxam on the entire larval development cycle of reproductive bees and conducted a comparative analysis, demonstrating that thiamethoxam significantly alters ecdysone [a hormone that controls molting in insects] and juvenile hormone titers [hormones for insect growth] in both queen and drone larvae, impairing metamorphosis and reproductive development,” the authors state. Risk assessments and scientific literature focus primarily on honey bee workers, rarely including how pesticides can impact queen and drone bees that are necessary for stable colonies. In focusing on this data gap, the researchers reveal that the survival rate of bee larvae decreases gradually with increasing doses of thiamethoxam, adding to the wide body of science on pesticide-related threats to honey bee health. (See Beyond Pesticides’ What the Science Shows on Biodiversity page for more information, as well as Daily News coverage on risk assessments here, here, and here.) Honey bees provide crucial ecosystem services as pollinating insects and play a vital role in […]

(Beyond Pesticides, September 17, 2025) A study in Environmental Science & Technology finds additive effects of a synthetic pyrethroid insecticide (cypermethrin) and two fungicides (azoxystrobin and prochloraz) on biological control, biomass of major invertebrate trophic groups (position in food web), and soil ecosystem processes in arable systems (land suitable for growing crops). The study authors further highlight the failure of pesticide regulations to consider elaborate trophic interactions and pesticide mixtures, as well as additive and synergistic effects within their assessments, calling attention to the complexity of real-world exposures and the lack of research to fully understand the implications of chemical use for agricultural and land management purposes. “Arable systems have a high dependence on diverse natural biota to support pest control, soil bioturbation, and nutrient recycling,” the researchers write. These communities rely on a balance of organisms within various trophic levels in order to function and provide vital ecosystem services. Disruptions caused by environmental contaminants, such as pesticides to nontarget organisms, impact entire ecosystems and overall biodiversity. As the authors state, current risk assessments underestimate the real-world risks of petrochemical pesticides and synthetic fertilizers that, despite a wide body of science connecting exposure to deleterious health and environmental effects, are […]

(Beyond Pesticides, September 16, 2025) As reported in the Daily News on August 28, the U.S. Environmental Protection Agency (EPA) announced that it “will hold a public webinar [today], September 16, 2025, at 2:00 PM ET to provide information on the ecological runoff/erosion and spray drift mitigation measures that can be used to protect endangered species from pesticides.” This follows closely behind an earlier announcement of a newly released Pesticide App for Label Mitigations (PALM) mobile tool to assist in implementing these mitigation measures. Despite boasting that the PALM tool is a “one-stop shop” for farmers to use EPA’s mitigation menu, which the agency claims helps to protect nontarget species, environmental critics say that self-directed mitigation without a rigorous reporting and enforcement apparatus fails to meet the level of protection that is necessary under the Endangered Species Act (ESA). As Beyond Pesticides has often reported, mitigation measures are not enforced through recordkeeping, inspections, and certification, and require no accountability from farmers and pesticide applicators. At the same time, EPA assumes compliance with mitigation measures as the basis for meeting statutory standards of reasonable risk from harmful chemicals, despite documented health and environmental harm. As a Daily News article earlier this […]

(Beyond Pesticides, September 15, 2025) With residues of the widely used weed killer glyphosate (Roundupᵀᴹ) in the food supply long documented, scientific attention has turned to the synergistic effects of the weedkiller— a magnified effect greater than the individual chemical effects added together. The authors of an article in World’s Poultry Science Journal write, “The synergistic toxic effects of commercial glyphosate formulations and their bioaccumulation in animal tissues are often overlooked in current safety assessments.” Following up on a previous action, Beyond Pesticides is telling Congress and the U.S. Environmental Protection Agency (EPA) that the agency must consider the effects of pesticides in the context in which they are used and promote the organic alternative.  Glyphosate residues in animal feed, as well as in water and through other exposure routes from food generally and residential areas, pose risks to both animal and human health, as these residues can bioaccumulate. As previously examined by Beyond Pesticides, the effects of pesticides are not limited to the crops to which they are applied. Synergistic effects of multiple chemical exposures are the rule, rather than the exception.   With poultry, the herbicide enters the production system through residues in genetically engineered feed. An earlier article in Scientific Reports concludes that glyphosate’s […]

(Beyond Pesticides, September 10, 2025) Published earlier this year, a review of over 1,700 studies in Nature Communications finds pesticides affect a diverse range of nontarget organisms and contribute to global biodiversity loss. The authors* reveal “negative responses of the growth, reproduction, behaviour and other physiological biomarkers within terrestrial and aquatic systems” for nontarget plants, animals, and microorganisms. “To our knowledge, there has been no systematic and overarching synthesis of how different types of pesticides affect the diversity of multiple non-target eukaryotic and prokaryotic organisms across all trophic levels,” the researchers write. They continue, “Furthermore, current syntheses have not considered how the impacts of pesticides differ globally across climatic zones or for major mechanisms of exposure, such as those acting in aquatic or terrestrial environments.” In particular, pesticide regulatory risk assessments analyze a limited range of model species, including rats, zebrafish, clawed frogs, honeybees, and earthworms, among others. As such, they are unlikely to capture the variety of responses to pesticide exposure seen across the diversity of species and communities found in both managed and natural systems,” the authors state. *Authors include Beyond Pesticides 2023 National Forum speaker Dave Goulson—see the Daily News on his keynote address here. Research Results […]

(Beyond Pesticides, September 8, 2025) Beyond Pesticides today called on Congress to require the U.S. Environmental Protection Agency (EPA) to incorporate real world science into its evaluation of pesticide safety calculations by recognizing that daily exposure involves multiple chemicals and synergistic interactions— a magnified effect greater than the individual chemical effects added together. The organization cites numerous scientific studies that call public attention to this issue; that a realistic assessment of the human and environmental harm potentially caused by pesticides cannot be evaluated based on single-chemical, single-species tests. Given the numerous complexities associated with this type of assessment, the group points to organic land management in agriculture and residential areas as a more cost-effective approach, sending this message to Congress: EPA must consider the effects of pesticides in the context in which they are used and with reference to the organic alternative. A recent study, covered by Beyond Pesticides in its Daily News, found that the presence of Varroa mites in combination with the neonicotinoid insecticide imidacloprid increases the risk of bee mortality and disrupts the larval gut microbiome. The study found synergy (a greater combined effect) between Varroa destructor, a parasitic mite that attacks and feeds on honey bees, and imidacloprid. The findings were published last […]

(Beyond Pesticides, September 4, 2025) A review of agricultural neonicotinoid insecticide regulations, published in Pest Management Science, evaluates the varied approaches being taken for bans and exemption-based restrictions in the European Union (EU), Canada, and the United States (U.S.). Despite an ever-growing and overwhelming body of science linking neonicotinoids (neonics) to adverse effects on pollinators and other nontarget species, the regulations fall short in protecting the environment and wildlife. The review, with the history and current status of neonics, lends further support for a full transition to organic agriculture and land management that removes neonicotinoid exposure routes and subsequent health threats. With the application of this widely used class of neurotoxic system insecticides increasing, so too has the concern over the long-term chronic effects on pollinators and other species from exposure. This concern, backed by scientific literature, has “led to increased governmental regulations since the mid-2010s, particularly in agricultural settings,” state the authors from Iowa State University and Washington State University. They continue, “These regulations have varied in terms of approach, geography, and timeline, starting with a ban implemented by the European Union (EU) and evolving into exemption-based regulations across two Canadian provinces and five U.S. states as of this […]

(Beyond Pesticides, September 3, 2025) A study in Environmental Entomology shows that habitat and open space near agricultural fields become a killing field of pesticides, threatening biodiversity due to contamination from toxic drift. The study detected 42 pesticides, including several neonicotinoids, which are among the most lethal threats to pollinators. The research reveals the complexity of pesticide flow through the environment and the inadequacy of current methods of protecting nontarget organisms, including honey bees, bumblebees, and hundreds of other species of native bees worldwide. Their catastrophic declines is tied to pesticides in large part and highlights the inadequacy of current pesticide reduction strategies, such as integrated pest management (IPM) and now other loosely defined concepts like “regenerative,” in an attempt to protect the environment and nontarget organisms in chemical-dependent land management and agriculture. (See What the Science Shows on Biodiversity.) The researchers on the study, from the U.S. Department of Agriculture, Cornell University and Michigan State University, put silicone bands on fence posts in open areas adjacent to highbush blueberry fields on 15 farms in western Michigan. Silicone takes up chemicals in the atmosphere which can then be extracted and analyzed. The fence posts were placed at seven intervals ranging […]

(Beyond Pesticides, September 2, 2025) It did not go without notice to U.S. grassroots environmental and public health advocates that earlier this month, over two million people in France signed a “first of its kind” petition that ultimately prevented the overturning of the country’s ban on bee-killing neonicotinoid insecticides. The action was widely covered in France, including in Le Monde. This uprising, organized by 23-year-old French master’s student Eleonore Pattery, emphasizes the importance of individuals in communities mobilizing people to protect the planet from pesticides that are having a devastating adverse effect on health and the environment. The grassroots push in France taps into a deep public concern about health and the environment that is emblematic of the level of public engagement needed to thwart the high level of chemical industry, agribusiness, and allied corporate influence that undermines basic protections. Industry interests have long been embedded in federal environmental and public health laws. For example, federal and state pesticide laws (the Federal Insecticide, Fungicide, and Rodenticide Act and similar state laws) allow widespread exposure to toxic chemicals despite the availability of nontoxic alternatives that are both efficacious and cost-effective. Without public engagement, as seen in France, significant improvements in law are constantly […]

(Beyond Pesticides, August 27, 2025) A study published in European Journal of Agronomy finds that “organic farming equals conventional yield under irrigation and enhances seed quality in drought, aiding food security.” For decades, organic advocates have heard from defenders of chemical-intensive agriculture that organic farming is not commercially attainable for widespread adoption and cannot compete on productivity and profitability at a commercial scale. At the same time, chemical manufacturers, chemical-dependent farmers, and their allies greenwash their products (e.g., active ingredients, full formulations, and pesticide-treated seeds) and practices by insisting in regulatory comments, contract science studies, and lobbying campaigns that they are necessary for climate-smart, sustainable, regenerative, and/or integrated pest management agriculture and land management. In this context, the chemical industry alliance is now pushing deregulation, preemption of state and local authority to restrict pesticides, and immunity from lawsuits for the harm caused by their products and practices. An expansive coalition of farmers, farmworkers, conservationists, medical professionals, Indigenous communities, and environmental and public health advocates is fighting back, including Beyond Pesticides. Background and Methodology The researchers tested twelve common bean genotypes of Phaselous vulgaris L., with eight local [Basque Country] landraces (defined by Oxford Language as “a local cultivar [plant] or […]

(Beyond Pesticides, August 22, 2025) Legislative language moving through Congress—intended to prevent farmers, consumers, and workers from holding pesticide manufacturers accountable for the harm caused by their toxic products—is being opposed by a broad coalition of farmers, beekeepers, consumers, environmentalists, and workers with the release today of a joint statement opposing a dramatic change in a fundamental legal right. The document, Protect the Right of Farmers, Consumers, and Workers to Hold Pesticide Companies Accountable for Their Harmful Products, is joined by 51 organizations, coalitions, businesses, and leaders representing tens of thousands of members and communities. The legislation at issue is hidden in a provision of the Appropriations bill (Section 453) that has passed through the Appropriations Committee in the U.S. House of Representatives and is headed for a vote of the full House in the next couple of weeks, followed by the U.S. Senate. The Appropriations provision is being pushed by chemical companies in the wake of extraordinary jury verdicts against Bayer/Monsanto, amounting to billions of dollars in compensatory and punitive damages, for “failure-to-warn” liability claims involving glyphosate (Roundupᵀᴹ) weed killer products. The pesticide has been classified as cancer-causing by the International Agency for Research on Cancer (a part of […]

(Beyond Pesticides, August 21, 2025) The presence of Varroa mites in combination with the neonicotinoid insecticide imidacloprid increases the risk of bee mortality and disrupts the larval gut microbiome, according to a study of the synergy (a greater combined effect) between Varroa destructor, a parasitic mite that attacks and feeds on honey bees, and imidacloprid. The study in Pesticide Biochemistry and Physiology adds to the growing body of science on the severely declining bee population by investigating the toxic effects of both the parasites and pesticide stressors in honey bees (Apis mellifera). “Given that V. destructor may increase bees’ sensitivity to imidacloprid by compromising their physiological health and immunity, this study systematically assesses the effects of V. destructor infestation and imidacloprid exposure on honey bee survival, detoxification enzyme activity, and gut microbiota,” the authors explain. The intestinal tract and gut microbiome are crucial for digestion, metabolism, nutrient absorption, immune regulation, and pathogen defense. Within honey bees, the gut microbiome is “highly susceptible to external environmental stressors, such as pesticide exposure and parasitic infections [and] these disturbances can lead to microbial imbalances, ultimately affecting bee health.” (See studies here and here.) Previous research earlier this year, captured in Daily News Variability […]

(Beyond Pesticides, August 20, 2025) As a part of a nationwide push to stop the use of petrochemical pesticides and fertilizers, Beyond Pesticides, in partnership with the City of Excelsior, Minnesota, and Osborne Organics, announced the transition of city park land sites to organic land management. Under its program, Parks for a Sustainable Future, Beyond Pesticides underwrites the development of organic transition plans and staff training on holistic practices. The goal of the program is to advance practical, resilient, cost-effective management techniques that confront urgent threats to public health, biodiversity, and climate that are exacerbated by toxic pesticide and fertilizer use. See the link to our press release here.  Excelsior City Councilmember Jennifer Caron said, “Excelsior has embarked on an exciting first step in organically managing our public parks and minimizing runoff into the lake.” Ms. Caron added: “By participating in the Parks for a Sustainable Future grant program with Beyond Pesticides, the city is learning how to eliminate herbicides, insecticides, and other pesticides on sites in the Commons, including the Ballfield and Great Lawn. The result will be a healthier Commons, particularly in areas heavily used by people, pets, and pollinators alike.”   Kevin Quinn, parks and natural resources manager for Excelsior, said: “Working with […]

(Beyond Pesticides, August 12, 2025) Last week on August 9, the United Nations observed International Day of the World’s Indigenous Peoples, a critical acknowledgement of Indigenous “food sovereignty, food security, biodiversity conservation and climate resilience,” as outlined in the report of the Expert Mechanism on the Rights of Indigenous Peoples, Eighteenth Session (July 14–18, 2025). As the report states, under Article 20 of the UN Declaration on the Rights of Indigenous Peoples, “Indigenous Peoples possess distinct economic systems rooted in traditional knowledge, practices and resources and have the right to sustain, strengthen and develop these systems in accordance with their cultures, traditions, values and aspirations.” It continues, “When deprived of their means of subsistence and development, this article provides that Indigenous Peoples are entitled to just and fair redress.” In a statement recognizing the importance of the day, Special Rapporteur on the rights of Indigenous Peoples, Albert K. Barume, focuses on the need for Artificial Intelligence (AI) to recognize that, “Indigenous Peoples have long been stewards of knowledge, biodiversity, and sustainable living [and] [w]ithout their meaningful participation, AI systems risk perpetuating historical injustices and deepening the violation of their rights.” Meanwhile, the current U.S. administration has shifted away from federal […]

(Beyond Pesticides, August 6, 2025) A study published in Science of The Total Environment finds that “chronic pesticide exposure alters metabolism and impairs fish growth and health.” With increasing concern about the long-term consequences of pesticide persistence in ecosystems, the scientific literature continues to expand the body of research findings on adverse effects, including impacts on marine or aquatic ecosystems and organisms. Given the known and growing risks, there is an ongoing movement to move beyond petrochemical-based chemicals for agriculture and land management by adopting policies and programs that advance organic criteria and principles, as outlined in national organic law and practiced by tens of thousands of certified farmers and land managers across the country, and even more at the international level. Background and Methodology “The objective of this study was to assess the physiological responses of juvenile P. lineatus exposed to environmentally relevant pesticide mixtures by integrating multiple biological endpoints across sub-individual and organismal levels,” the authors write. The study was conducted at two sites in the Tibagi River watershed located in Paraná, a southern region in Brazil. There was a reference site (RFS) and an agricultural site (AGS), the former having minimal pesticide contamination and the latter having […]

(Beyond Pesticides, July 31, 2025) A study published in Environmental Advances finds that hundreds of honeybee hives across central and northern Italy are contaminated with various pesticides and their metabolites, including glyphosate and fosetyl.  “There was no significant difference in glyphosate presence between dead/dying and live bees, suggesting chronic exposure rather than acute toxicity. However, higher pesticide concentrations in dead/dying bees indicate potential sublethal effects contributing to colony distress,” according to the authors. This peer-reviewed study builds on the mounting evidence outlined in the literature connecting pesticide residues to nontarget harm to pollinators and other insects and animals that are critical to biodiversity. Background and Methodology “The primary objectives of this study were to develop and validate a reliable, sensitive method for analyzing polar pesticides [highly soluble in water] in honeybees and to investigate polar pesticides residue levels in honeybees across northern and central Italy,” say the researchers of this study, who conduct research at the Experimental Zooprophylactic Institute of Lombardy and Emilia Romagna “Bruno Ubertini”, Experimental Zooprophylactic Institute of Umbria and Marche “Togo Rosati”, and Experimental Zooprophylactic Institute of Lazio and Tuscany “M. Aleandri.” 314 honeybee samples were gathered voluntarily from local beekeepers in six regions of northern and […]

(Beyond Pesticides, July 18, 2025) A study in Royal Society Open Science shows intraspecific differences (between individuals of a species) in wild bumblebees (Bombus vosnesenskii) exposed to an herbicide (glyphosate), a fungicide (tebuconazole), and an insecticide (imidacloprid), with gut microbiome health as a factor. “Wild pollinator declines are increasingly linked to pesticide exposure, yet it is unclear how intraspecific differences contribute to observed variation in sensitivity, and the role gut microbes play in the sensitivity of wild bees is largely unexplored,” the authors explain. “Here, we investigate site-level differences in survival and microbiome structure of a wild bumble bee exposed to multiple pesticides, both individually and in combination.” In collecting 175 individuals of this wild, foraging species from an alpine meadow, a valley lake shoreline, and a suburban park and exposing them to a diet with individual pesticides and mixtures, the researchers assess the varying lethal and sublethal effects that can occur with pesticide exposure. Between the three sites, the survival differences “emphasize the importance of considering population of origin when studying pesticide toxicity of wild bees” and highlight how pesticide sensitivity not only varies between species but within individuals of the same species with site-specific impacts. (See previous Daily […]

(Beyond Pesticides, July 17, 2025) The widespread use of pesticides year-after-year, decade-after-decade, has been found to lead to unintended consequences not only for public health but also for broader ecosystem stability and biodiversity. These impacts include potential nontarget harm through adverse developmental and reproductive effects on the vinegar fly, Drosophila melanogaster, the subject of a peer-reviewed study in Royal Society Open Science. The authors, who studied the organochlorine fungicide chlorothalonil, conclude, “Chlorothalonil exposure decreases larval survival, extends developmental duration and reduces fecundity.” “Even at the lowest tested concentration, chlorothalonil exposure resulted in reduced body weight, ovariole count and egg production compared with non-exposed individuals,” the researchers find. This study builds upon years of scientific research findings and critiques of existing federal pesticide law, as well as the U.S. Environmental Protection Agency’s (EPA) failure to fully assess the adverse impacts on biodiversity and ecosystem stability during the pesticide registration review process. Methodology and Background The goal of this study is to evaluate the health impacts on a nontarget insect species (Drosophila melanogaster) from chronic exposure to chlorothalonil. This specific fungicide was chosen for various reasons, including its wide use across cereals, vegetables, and fruits; evidence linked to adverse health effects on […]

(Beyond Pesticides, July 16, 2025) A study following a mass mortality event of approximately 200 monarch butterflies (Danaus plexippus plexippus) in Pacific Grove, California, highlights the role of pesticides, synthetic pyrethroids in particular, in causing lethal and sublethal effects to nontarget organisms. The research, published in Environmental Toxicology and Chemistry, detects residues of 15 pesticides and associated metabolites in the bodies of 10 deceased butterflies collected from the January 2024 event that occurred near an overwintering site frequented by monarchs. “On average, each monarch butterfly contained 7 pesticides,” the authors report. They continue, “Notably, three pyrethroid insecticides—bifenthrin, cypermethrin, and permethrin—were consistently detected at or near each chemical’s lethal dose (LD50).” LC50, or Lethal Concentration 50, values represent the concentrations of chemicals lethal to 50% of a test population. To assess pesticide residues within ten of the deceased butterflies, the researchers use liquid and gas chromatography with tandem mass spectrometry (LC-MS/MS and GC-MS/MS) and find “a total of 15 pesticides and associated metabolites in the butterflies, including 8 insecticides (plus 1 associated metabolite), 2 herbicides (plus 2 associated metabolites), and 2 fungicides.” The study “present[s] evidence that the mortality incident at the Pacific Grove Monarch overwintering site was likely caused by […]