(Beyond Pesticides, May 24, 2024)
Even allegedly “low-toxicity” pesticides such as flupyradifurone (insecticide), azoxystrobin, and difenoconazole (fungicides) pose adverse health effects to solitary ground-nesting squash bees (Xenoglossa pruinose), according to a study published in Biological Sciences. Fungicide exposure led to less pollen collected per flower, while exposure to flupyradifurone (FPF) produced larger offspring (which make it more challenging for them to fly). Simultaneous exposure to the three pesticides “induced hyperactivity in female squash bees relative to both the control and single pesticide exposure, and reduced the number of emerging offspring per nest compared to individual pesticide treatments.” With United Nations Food and Agriculture Organizations-sponsored World Bee Day earlier this week, now more than ever advocates are calling for the elimination of toxic insecticide classes, such as neonicotinoids and butanolides, and their wholesale replacement with organic land management principles.
This study was written by Sabrina Rondeau, PhD, postdoctoral Fellow in the Department of Biology at the University of Ottawa, and Nigel E. Raine, PhD, professor at University of Guelph’s School of Environmental Science. Published on March 20, 2024, the researchers delve into the individual and co-exposure impacts of two fungicides and one insecticide, which is important, given the documented synergistic effects of chemical mixtures cited in other peer-reviewed, scientific studies.
The researchers used “10 hoop houses covered with bee-proof mesh and divided in the middle by a flexible wall made from transparent, colorless polyethylene plastic sheeting to obtain 20 experimental units” alongside Lakefield, Ontario, Canada in 2020. The site was sprayed with flupyradifurone and the two fungicides one week before the squash bees were introduced to their hoop houses. None of the pesticides were sprayed the following year. Over the three weeks of the experiment, Drs. Rondeau and Raine gathered data on nesting activity, foraging activity, motor activity, crop yield and flower counts, offspring production, and pesticide residues. Regarding the results specifically for the fungicides, “[o]n average, female squash bees collected 32% less pollen per single flower visit () and spent 24% less time handling squash flowers () in enclosures treated with Quadris Top [azoxystrobin and difenoconazole].” Regarding chemical mixture of Sivanto (FPF) and Quadris Top, “Computing simple main effects of pesticide treatments revealed that the mean number of offspring that emerged per nest was significantly lower for bees that were exposed to both pesticides compared to those that were only exposed to either [pesticide product.]”
This is not the first time that neonicotinoid insecticides have been found to have adverse effects on pollinators and other living organisms, including humans. The U.S. Environmental Protection Agency (EPA) registered FPF in January 2015, deeming the insecticide safer than on-the-market neonicotinoids such as imidacloprid, even though their own field studies reveal high mortality in adult bees within 24 hours of treatment.
The European Union followed suit, with the Directorate-General for Health and Safety authorizing its approval in November 2015 in spite of advocates warnings of its hasty roll-out. Organizations including Beyond Pesticides have taken action by advocating for the passage of Saving America’s Pollinators Act in 2019. Groups such as Center for Biological Diversity have engaged in litigation on Bayer’s proposal to EPA to permit expanded use of FPF on over 300,000 acres of tobacco-growing land nationwide in 2018. A 2020 study published in PLOS One affirms the concerns of pollinator friends, finding that FPF and sulfoxaflor were found to increase cell death (apoptosis) and oxidative stress in honey bees. Another study also published in 2020 in Biological Sciences found that FPF has the same mode of action as neonics, with potential to remain in the soil for months or years after its original application.
Difenoconazole, meanwhile, has been found to have possible links to an increase in cancer (possible carcinogen) and suspected endocrine disruption. Additionally, a 2023 study published in Journal of Agricultural and Food Chemistry found that strawberries sprayed with this fungicide reduced their flavor and fragrance, posing implications for the economic wellbeing of strawberry farmers who remain on the chemical treadmill. Azoxystrobin also has adverse health effects on humans, including eye irritation and nutrient absorption disruption, as well as potential toxicity to aquatic organisms due to algae blooms, permanence in groundwater, and leaching from soil into living organisms. Among the over 2,000 samples tested for the U.S. Food and Drug Administration’s 2020 Pesticide Residue Monitoring Report, 185 different pesticide residues were detected; of that 185, the fungicide azoxystrobin appeared the most frequently (146 times). Litigation on azoxystrobin has challenged its use on a New York State golf course and EPA fined Syngenta $1.2 million for, among other reasons, the pesticide company’s failure to maintain study records used for the pesticide’s registration—as required by the Federal Insecticide Fungicide and Rodenticide Act (FIFRA)—that characterized the food residues resulting from the use of azoxystrobin and propiconazole. For more information, see Daily News sections on neonicotinoids, pollinators, and chemical mixtures. See also the adverse effects of difenoconazole and azoxystrobin, as well the corresponding peer-reviewed scientific literature, in the Gateway on Pesticide Hazards and Safe Pest Management.