Lawmakers may give Minnesota cities the power to ban pesticides that are killing pollinators, mayflies and other insects.

The proposed law, which comes as native bumblebee and butterfly populations are falling throughout the state, would target widely used lawn care products containing neonicotinoids and all other pesticides labeled "pollinator-lethal" by the Minnesota Department of Agriculture.

"Pollinators need habitat that is free from pesticides," said Rep. Samantha Vang, DFL-Brooklyn Center, who wrote the proposed law. "Cities could be that safe place for bees, butterflies and all sorts of other critters that make our great outdoors the place we want it to be."

Pesticides are regulated by the Department of Agriculture, giving individual cities little say over what chemicals can be used within their boundaries. If enacted, the department would keep a list of pesticides lethal to pollinators on its website. Each city could issue a blanket ban on the pesticides included in the list.

Legislators proposed a similar law in 2020 but failed to enact it.

Researchers aren't sure exactly how far pollinator populations have collapsed over the past two decades, as neonicotinoids became the dominant pesticide used on farms and lawns. But studies on individual species show the drop has been drastic.

More than 90% of rusty patched bumblebees, Minnesota's state bee, have died off since the late 1990s, and the species has disappeared from more than 99% of its native range. It is now seen only in a handful of places, including around the Twin Cities.

Monarch butterflies' numbers have also fallen by more than 80% since the 1990s. Populations of mayflies, a food source for fish, birds and bats, have been cut in half in the past 12 years.

Pesticides, disease and habitat loss are likely the main causes of the declines, according to the U.S. Fish and Wildlife Service.

Several uses of neonicotinoids and other pesticides would still be allowed even if a city were to adopt a ban. Pet care products, such as in tick and flea prevention, would be exempt. So would sprays that target lice, bedbugs and indoor pests, as well as any chemicals used by mosquito control districts.

Logistical questions, such as how the bans would be enforced, would need to be ironed out before the Department of Agriculture would support the change, Assistant Commissioner Whitney Place told lawmakers at a committee hearing.

Greg Stanley • 612-673-4882