Cutting back on roadside mowing in Iowa to help pollinators

Declining numbers of butterflies, bees and other pollinators is drawing attention to management practices for roadside grasses, which some see as critical to restoring the insect populations.

'Definitely with the decline in honey bees, native bees and the decline of Monarch butterflies, we need to get more habitat on the landscape, and better roadside mowing practices is one way to do it,” said Jennifer Hopwood, a pollinator conservation specialist for the Xerces Society.

The not-for-profit society is working with the U.S. Department of Transportation to reform roadside mowing practices around the country.

She said several examples of best practices are coming from Iowa, including a robust native plant program, a native seed market, limited use of herbicides in roadways and restricted mowing rules.

'Iowa is unique in native plant restoration work,” she said. 'It's a leader and ahead of the curve without a doubt.”

The Iowa DOT and county road crews, such as in Linn County, which has a roadside manager, use a variety of preservation practices.

But some believe more should be done.

Mowing is done to improve safety through visibility, control noxious weeds or brush and, to a lesser extent, for aesthetics, Hopwood said.

'If weeds are growing clear out to the road, it's hard to see, so we try to mow,” said Jerad Kelley, a maintenance foreman for Linn County Secondary Roads Department. 'There's not exact times. We get gravel roads mowed twice a year, and hard surface three times a year.”

Iowa restricts roadside mowing to after July 15, within 10 feet of the roadway, and generally allows only two to three mowings a year. State code regulates herbicides toxic to bees.

Harvesting hay from ditches along state roads is allowed after July 15, but a permit is required.

Compliance

Obtaining compliance from residents can be problematic, said Joy Williams, vegetation management agronomist for the Iowa DOT. They may want to mow along the roads for hay or aesthetic reasons or spray herbicides on wildflowers planted by the DOT or county thinking they are weeds, she said.

'We are seeing improved compliance, but it's not where it needs to be,” Williams said. 'If one farmer jumps in and mows in late June or early July, others will follow.”

Some advocates are critical of public agencies, saying they should do more.

Matt Baumann of Cedar Falls is an advocate of saving pollinators, and he writes a blog called Iowa Prairieman.

He has concerns that prime roadside mowing time between July and September also is the peak time for flowering of plants and butterfly breeding. He said during his commute on Interstate 380 from Cedar Falls to Cedar Rapids, he has noticed numerous patches of milkweed get mowed down 'like clockwork” around this time each year.

'This mowing is a catastrophic loss of monarch habitat that directly impacts monarch butterfly recovery and furthers their decline,” he said.

He'd like to see areas not targeted for mowing be allowed to grow unhindered, and to end the practice of mowing if aesthetics is the only reason, he said.

The Iowa DOT's Williams agreed that mowing when plants are flowering is disruptive to reproduction cycles, but then the question becomes when to mow. The ideal time would be after the first frost, but crews are busy preparing for fall and winter.

Mowing early in the season could disrupt species such as pheasants or songbirds that nest in the ditches, Williams said.

'The laws were written years ago before there were big concern for monarchs, before the species was labeled as imperiled,” she said.

The state and its counties have planted a combined 100,000 acres of native grasses and wildflowers since 1998, Williams said. Despite that, the populations continue to suffer, she said.

The commercial honey bee population has declined 40 percent since 2006, with loss of biodiversity, destruction of habitat and pesticides as primary threats, according to Greenpeace International.

Only 56 million butterflies remain of what had been 1 billion in the 1990s, according to the Xerces Society.

Fish and Wildlife Service is leading a $20 million national effort to save the butterfly. Included is a plan to plant milkweed to

promote habitat growth, including through Iowa along the Interstate 35 corridor from Canada to Mexico.