08
Oct
Report Highlights U.S. Cities Facing Pollinator Declines Due to Multiple Pesticide Exposure
(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.â€
The report’s results underscore the pervasiveness of pesticide drift and dispel the myth that chemicals are only a problem in agricultural areas. Data has long shown that, while the volume of pesticide use in agricultural areas is the concentration of pesticide use per acre is higher in urban areas, “Homeowners use up to 10 times more chemical pesticides per acre in the urban environment than farmers’ usage on crops (US FWS, 2000),†according to a review in Science of The Total Environment. Toxic pesticides are employed for pest management in numerous nonagricultural public contexts, such as mosquito spraying, turf and athletic playing fields, public parks, and other common outdoor (and indoor) areas, as outlined in the scientific literature.
Background and Methodology
The “primary objective [of the study] was to describe the assemblage of pesticides that are present within urban landscapes and their field-realistic concentrations,†according to the authors. The researchers gathered samples from nineteen host plants in the spring of 2022 at 14 sites in California and 10 sites in New Mexico.
The sites include public parks and private yards or pollinator gardens, with volunteers from Native Plant Society and Master Gardeners offering access after a survey confirmed the suitability of the area based on previous/ongoing pesticide use.
At each site, leaf tissue was collected from between six to ten plants per species and stored at the Cornell Chemical Ecology Core Facility for safekeeping. A standardized pesticide extraction method (modified EN 15662 QuEChERS) screened for 94 pesticides (including metabolites or breakdown products) based on three criteria: extensive agricultural or residential use in the U.S., relevance to insects based on toxicity, and quantifiability via the selected methodology of liquid chromatography mass spectrometry (LC-MS/MS).
Data for county pesticide application reports were provided by Sacramento and Yolo counties, with county-specific data for Albuquerque not included due to a lack of availability at the date of the survey. Application data for California included “all pesticide applications made to support agricultural production except for seed treatments.†The authors continue: “They also include non-agricultural pesticide applications made to maintain roadside and railroad rights-of-way, parks, golf courses, cemeteries, and any application of a restricted material and/or made by a licensed pest control operator (e.g., landscaping or pest management professional). Consumer home-and-garden uses are not included.â€
The report was published on August 22, 2025, in Environmental Toxicology and Chemistry, a journal of Oxford University Press. Funding for this report included grants from the National Science Foundation and Carroll Petrie Foundation. The authors declared no conflicts of interest in writing this study.
Findings
As mentioned, the researchers found widespread contamination of host plants (314 out of 336) for butterfly populations and likely other beneficial insects and pollinators, with a mixture of detections reported on most plant samples spanning insecticides, fungicides, herbicides, one antibiotic, one degradate (breakdown product; think microplastic to plastic), and one adjuvant.
The following compounds (and their “familiesâ€) were screened and detected at least once across the samples:
- Fourteen Insecticides
- Chlorantraniliprole (Diamide)
- Methoxyfenozide (Growth Regulator)
- Clothianidin (Neonicotinoid)
- Imidacloprid (Neonicotinoid)
- Thiamethoxam (Neonicotinoid)
- Dinotefuran (Neonicotinoid)
- Acephate (Organophosphate)
- Carbaryl (Carbamate)
- Fipronil (Phenylpyrazole)
- Bifenthrin (Pyrethroid)
- Spirotetramat (Ketoenol systemic)
- Spinosad (spinosyn A/D) (Fermentation-derived)
- Pyriproxyfen (Juvenile hormone analog)
- Metaflumizone (Semicarbazone sodium channel blocker)
- Ten Herbicides
- Atrazine (Triazine)
- Ametryn (Triazine)
- Propazine (Triazine)
- Prometon (Triazine)
- Terbutryn (Triazine)
- Thiobencarb (Thiocarbamate)
- S-metolachlor (Chloroacetanilide)
- Oxyfluorfen (Diphenyl-ether)
- Pendimethalin (Dinitroaniline)
- Diuron (Substituted urea)
- Twenty Fungicides
- Azoxystrobin (Strobilurin)
- Pyraclostrobin (Strobilurin)
- Kresoxim-methyl (Strobilurin)
- Fluopyram (Succinate dehydrogenase inhibitor (SDHI)
- Boscalid (SDHI)
- Propiconazole (Triazole)
- Myclobutanil (Triazole)
- Tebuconazole (Triazole)
- Difenoconazole (Triazole)
- Triadimefon (Triazole)
- Chlorothalonil (Broad-spectrum)
- Mancozeb (Dithiocarbamate)
- Captan (Phthalimide)
- Thiabendazole (Benzimidazole)
- Thiophanate-methyl (Benzimidazole)
- Metalaxyl (Acylalanine)
- Iprodione (Dicarboximide)
- Fenhexamid (Hydroxyanilide)
- Cyprodinil (Anilinopyrimidine
- Pyrimethanil (Anilinopyrimidine)
- Oxypyrimidine degradate (insecticide)
- Fumagillin (Antibiotic)
- Adjuvant (Piperonyl butoxide)
“The good news is that everyone can help protect wildlife in urban spaces by eliminating at-home pesticide use,†says Anderson. He continues: “This study improves our understanding of the risks pesticides pose to butterflies in urban landscapes, and will allow us to improve our conservation efforts for these species.”
Azoxystrobin and chlorantraniliprole were highlighted as specific compounds of concern due to their significantly high level of detection and known toxicity to insects. Azoxystrobin was found in 84% of Sacramento samples, with 51 plants exceeding residue levels of 0.67 ppb (parts per billion), which the authors attribute to a field-realistic level known in previous studies to show reduced monarch wing size at this level. With half-lives ranging from 0.4 to 17.5 days and repeated applications being a common practice, researchers warn of prolonged exposure. At the same time, chlorantraniliprole was detected in 33 plants, with 7 plants exceeding monarch larval LC50 values—LC50 referring to the lethal concentration at which 50 percent of the population would likely perish from exposure.
Previous Research
The widespread contamination of farmland, waterways, and whole ecosystems with neonicotinoid insecticides, treated seeds, and associated products emphasizes a critical need for stricter pesticide regulations, according to environmental advocates.
Reports published in the last year from state and local governments (Wisconsin and Iowa, respectively) and in partnership with academic institutions and nonprofit organizations (Connecticut and Minnesota, respectively) on the prevalence of neonicotinoid contamination in their waterways and soils are deeply concerning. For example, a recent report from University of Connecticut, Neonicotinoids in Connecticut Waters: Surface Water, Groundwater, and Threats to Aquatic Ecosystems, published in partnership with University of Connecticut and Norwalk River Water Keeper earlier this year found that 46% of Connecticut waterway samples are contaminated with levels of the neonicotinoid insecticide imidacloprid—one of the most widely used insecticides in the U.S. on lawn and golf courses. (See Daily News here.)
The toxicity and pervasiveness of neonicotinoids are reinforced by peer-reviewed scientific literature. Scientists at the Institute of Biochemistry and Molecular Biology at Ulm University in Germany exposed embryos of South African clawed frogs (Xenopus laevis) to three neonicotinoids (imidacloprid, thiamethoxam, and its metabolite clothianidin), which led to developmental effects down to a molecular level. These frogs are a well-established model species often used in ecotoxicology studies as bioindicators for overall environmental and ecosystem health. When amphibian species like Xenopus laevis are exposed to contaminants in the water, it leads to negative impacts in the food chain and harms biodiversity. The study concludes that exposure to neonicotinoids directly or through contaminated water leaves entire ecosystems vulnerable. (See Daily News here.) Pesticide mixtures pose a serious threat to habitats and ecosystems surrounding agricultural fields, threatening crucial biodiversity hubs.
A study led by researchers at the U.S. Department of Agriculture (USDA), Cornell University, and Michigan State University detected 42 pesticides, including several neonicotinoids, such as imidacloprid and acetamiprid, at very high concentrations. One very significant result of the study is the finding that distance does not affect the number of active ingredients detected—in other words, just as many active ingredients are found at 32 meters from the field as at two meters. (See Daily News here.)
There is increased scrutiny on the failure of the pesticide registration process, as defined by the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), to adequately assess the health effects of pesticides—including neonicotinoids more broadly. An analysis published in Frontiers in Toxicology last year by Natural Resources Defense Council, Center for Biological Diversity, and Center for Food Safety, finds serious flaws in the EPA process based on the first comprehensive assessment of unpublished rodent-based developmental neurotoxicity (DNT) studies, conducted between 2000-2003 and submitted by pesticide manufacturers as part of the registration process. (See Daily News here.)
Call to Action
You can take action today by learning more about non-toxic alternatives to pest management through our programs on Mosquito Management and Insect-Borne Diseases, Nontoxic Lawns and Landscapes, and other resources based on your interest. See here to access additional Daily News and to learn more about the scientific literature on neonicotinoids and other pesticides, please see our What the Science Shows on Biodiversity webpage.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
