Nature Lab

Native Bee Management

Impacts of Neonicotinoids

When headlines warn of pollinator losses, many people think of declining European honeybees. But Missouri is home to around 450 species of native bees that also provide essential pollination services for food crops and native wildflowers.

In the last 20 years, farmers have turned to neonicotinoids — a relatively new class of pesticides that mimic nicotine and are highly toxic to insects — to enhance crop production and control pests. Scientists have grown concerned that neonicotinoid residues could harm wild bee communities.

Starting in 2017, a team of researchers, including scientists from MDC, the University of Missouri (MU), and the U.S. Geological Survey Missouri Co-op Unit, conducted a two-year field study to assess whether neonicotinoid seed treatments influenced wild bee abundance and richness.

In 2017 and 2018, the team, led by Anson Main of MU’s School of Natural Resources, planted 23 Missouri agricultural fields of soybeans using one of three seed treatments: untreated (no insecticide), treated with a neonicotinoid active ingredient known as imidacloprid, or previously treated. During both years, the team collected wild bees from the study’s field margins monthly from May to September. They also collected soil and flowers from fields and field margins.

Analysis showed that insecticide presence in soils and flowers varied over the study and that wild bee abundance and species richness were not significantly different among field treatments.

However, neonicotinoid presence in field soils was associated with significantly lower richness in ground- and above-ground-nesting wild bees.

“As 70 percent of wild bees nest in the ground and are valued pollinators, it is critical that we conserve our native bee populations,” Main said.

The study concluded that eliminating neonicotinoid use on wildlife management areas may help sustain viable, diverse wild bee populations.

Neonicotinoids and Wild Bees at a Glance

Highlights

• Neonicotinoids were detected in 39% of treated and previously treated fields.
• Field treatment had no significant effect on wild bee abundance or richness.
• Reduced species richness of wild bee guilds in fields with neonicotinoids present.
• Seed-treatment insecticides may negatively impact bee community conservation.

Learn more at short.mdc.mo.gov/Zso.