03
Dec
Studies Cite Risk Assessment and Regulatory Deficiencies in Protecting Ground-Nesting Bees
(Beyond Pesticides, December 3, 2024) In an article in Science, Sabrina Rondeau, PhD reviews her research from 2022-2024 showcasing species of ground-nesting bees, often found in crop fields, that are highly vulnerable to soil pesticide residues and subsequently suffer population declines. Dr. Rondeau, a postdoctoral fellow in the Department of Biology at the University of Ottawa, points to regulatory deficiencies, specifically in environmental risk assessments (ERAs), and the detrimental effects of pesticides on pollinators that threaten food security and biodiversity.
“Modern intensive agriculture faces a critical paradox: The very pesticides designed to protect our crops endanger essential pollinators that sustain their productivity,†Dr. Rondeau says in the article. Her research (see here, here, here, here, here, and here) identifies important gaps overlooked in current assessments and regulations for bee species, including the common eastern bumble bee (Bombus impatiens) and the hoary squash bee (Xenoglossa pruinosa). Bumble bee queens in temperate climates hibernate for 6-9 months in the soil, while the hoary squash bee is a solitary ground-nesting species. Reference additional Daily News coverage on ground-nesting bees here and here.
“‘Our findings show that over 70% of wild bee species, which are crucial for pollinating our food crops, face significant risks from pesticide residues in soil—a threat current regulations overlook,’ says Dr. Rondeau†in a news release. See additional coverage on soil pesticide residues here, here, and here.
In reflecting on one study, Dr. Rondeau shares, “I generated the first field exposure estimates for overwintering bumble bee queens to pesticide residues in agricultural soils. I identified high risks of exposure to multiple pesticide residues for bumble bee queens that overwinter in agricultural soils in eastern Canada, especially in apple orchards. Orchard soils at suitable overwintering sites contained mixtures of up to 29 pesticides, and 95% of samples contained at least one insecticide, herbicide, and fungicide.†This study highlights the extent to which ground-dwelling bee species can be exposed to a multitude of pesticides.
In this experiment, “newly emerged bumble bee queens were offered numerous boxes of soil treated with different pesticides, alongside untreated soil, within large mesh-covered enclosures.†The bumble bee queens “were seemingly attracted to pesticide-contaminated soils. This apparent preference increases their likelihood of exposure to and potential risk from pesticide residues while they overwinter underground,†Dr. Rondeau states.
In another study, size-dependent effects are noted for bumble bee queens exposed in soil applied with the broad spectrum insecticide cyantraniliprole. The results indicate that queens that are heavier exhibit increased mortality, delayed brood emergence, and smaller offspring. Dr. Rondeau concludes that, “These larger queens likely face greater vulnerability to cyantraniliprole because of their greater muscle mass (cyantraniliprole disrupts insect muscle function), greater surface area in contact with soil, and lower metabolic detoxification capacity. My findings suggest that cyantraniliprole impairs heavier queens’ ability to feed their brood and highlight potential cascading impacts on bumble bee populations, as larger queen size is key to successful overwintering and colony establishment in the spring.â€
Lastly, female squash bees show reduced pollen collection with fungicide exposure to a product containing azoxystrobin and difenoconazole, while coexposure to the insecticide flupyradifurone with the fungicide “synergistically induced hyperactivity and reduced the number of offspring that emerged from each nest,†Dr. Rondeau states. “These results highlight potentially serious consequences for squash bees,†she concludes, noting that “reduced offspring production per nest due to pesticide coexposure could contribute to population declines.â€
ERAs are meant to assess agrochemicals, leading to regulatory approval for only those that pose low environmental risks. Yet, there is a wide body of science that highlights adverse effects on critical pollinator species from pesticides on the market. Current ERAs fail to adequately protect these organisms, as they rely on studies with specific model species to reflect the risks for all species. The U.S. Environmental Protection Agency (EPA) primarily focuses on the western honey bee (Apis mellifera), the differing exposure and subsequent effects experienced by other species are disregarded.
“[W]hereas most of the world’s 20,000+ bee species are solitary, honeybees live in large colonies that benefit from social detoxification strategies, which buffer pesticide impacts,†Dr. Rondeau says. She continues, “Failures to detect and document pesticide impacts on wild bees arise from multiple other deficiencies, which include incomplete consideration of potential long-term and sublethal effects, overlooked exposure routes specific to wild bees, and failures to account for possible coexposure to multiple pesticides.†See more on EPA failures here, here, here, and here.
A wider range of bee taxa needs to be considered in risk assessments to better protect all vital pollinators. As previously covered by Beyond Pesticides, pesticide sensitivity varies greatly between species. Relying on a single species to determine risks to all bees is negligent on the part of regulatory agencies. What is considered “low toxicity†for one species can be highly lethal for another.
As an alternative to harmful petrochemical pesticides, methods for crop protection can consider pollinator preservation, which in turn protects food security and biodiversity, by employing strategies for organic land management. As Dr. Rondeau states, “My research reveals a clear potential for ground-dwelling bees to be affected by field-realistic (co)exposure to soil pesticide residues. These findings urgently call for a reassessment of global pesticide regulations to create a safer, more sustainable agricultural future that protects both our crops and the pollinators they rely on.â€
Organic agriculture is the solution that not only eliminates exposure to toxic synthetic pesticides for pollinators, including ground-nesting bees, but it also supports soil health and the health of all organisms, including humans. In previous coverage, Beyond Pesticides reports how researchers find that organic farming provides the highest benefit to bees, as organic practices lead directly to lower parasite load and higher colony growth.
See more on the benefits of organic land management here, as well as options for least-toxic control of pests with ManageSafe™. Make The Safer Choice to avoid hazardous home, garden, community, and food use pesticides, and learn about Eating with a Conscience by choosing organic food to protect health and the environment.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source:
Rondeau, S. (2024) Digging below the surface: Hidden risks for ground-nesting bees, Science. Available at: https://www.science.org/doi/10.1126/science.adt8998.
