Bee alert: Pesticides pose a real threat to more than 70% of wild bees

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A new study reveals alarming risks that pesticides pose to ground-nesting bees, which are crucial for pollination and food production. As agriculture increasingly relies on pesticides to protect crops, the unintended consequences for these essential pollinators are becoming clearer.

Led by Sabrina Rondeau, an NSERC Postdoctoral Fellow in the Department of Biology at the University of Ottawa, the research highlights the urgent need to reassess pesticide safety standards to protect these essential pollinators. The work is published in the journal Science.

The study reveals that current pesticide risk assessments, which primarily use honeybees as test subjects, fail to account for the unique vulnerabilities of wild bees that nest in soil. "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.

The study's key discoveries include:

1. Bumble bee queens may be attracted to pesticide-contaminated soils, increasing their exposure during critical overwintering periods.
2. Exposure to certain pesticides in soil, particularly cyantraniliprole, reduce survival and reproductive success in bumble bee queens, potentially impacting future generations.
3. For squash bees, exposure to combinations of insecticides and fungicides disrupts behavior and lowers offspring production, signaling potential population declines.

"We found that larger bumble bee queens, typically more likely to survive winter and establish successful colonies, were paradoxically more vulnerable to pesticide exposure," Dr. Rondeau explains. "This could have cascading effects on bumble bee populations."

The research employed a combination of field and laboratory studies, starting with quantifying pesticide residues at suitable hibernation sites for bumble bee queens on Ontario farms. These field exposure estimates informed subsequent studies on the impact of such exposure on hibernating bumble bee queens and the hoary squash bee, a solitary ground-nesting species.

"Our work demonstrates that protecting wild pollinators requires a fundamental rethinking of how we assess pesticide safety," Dr. Rondeau concludes. "It's crucial for safeguarding both our food systems and biodiversity."

This research underscores the need for comprehensive reforms in pesticide regulations to ensure the protection of all pollinator species, particularly those nesting in agricultural soils.

More information: Sabrina Rondeau, Digging below the surface: Hidden risks for ground-nesting bees, Science (2024). DOI: 10.1126/science.adt8998

Journal information: Science

Provided by University of Ottawa