Wisconsin officials aim to keep invasive Japanese stiltgrass from spread in state

Jack Albright

Milwaukee Journal Sentinel

USA TODAY NETWORK – WISCONSIN

On Aug. 11, the University of Wisconsin-Madison Extension Forestry team had one confirmed case of the invasive Japanese stiltgrass in Rock County, Wisconsin, and alerted people to be on the lookout in a news release.

Seven days later, it has confirmed one more case in the state and is looking into a suspected third.

It’s a cause for concern for Mark Renz, UW-Madison Extension Weed Specialist and professor in the Department of Plant and Agroecosystem Sciences, who understands the dangers of Japanese stiltgrass.

'It can damage these forest systems in several ways,' Renz said.

Because it can grow in shaded areas, Japanese stiltgrass can grow a lot of biomass and cover large portions of forest floors, so you end up with 'seas of grasses' in forests, Renz said.

That does three things.

First, it competes with native plants and wildlife habitats. Second, which may be less well-known, it dries up forests, increasing the frequency of fires. And third, it can change the soil biota, which can alter how nutrients get broken down, disrupting an ecosystem.

'All of those things add up into a pretty bad situation,' Renz said.

Its destructive capabilities are why it’s so important to Renz and the rest of his team not to let the invasive species spread uncontrollably.

More common in southern Illinois, but spreading into parts of northern Illinois, Japanese stiltgrass has been on Renz’s radar before the initial discovery last month.

It spreads by seed, so if those plants are growing in a waterway, it can push seeds downstream to new areas. But Renz said the most common way it spreads is by getting onto shoes or lawn equipment in an infested area, and being moved accidentally that way.

'We think that’s how the initial population got established at this one site in Rock County,' Renz said.

The UW-Madison Forestry news release said Japanese stiltgrass grows horizontally on the ground, anywhere from a half-foot to 3 feet in length. It has a thin, weak root system and has rootlets emerging from nodes along the lower sections of the stem.

In the release, there are guides and videos to identifying the invasive plant.

If you think you found Japanese stiltgrass, the Forestry team recommends the following:

•Take close-up photos of the grass as well as mid-range and zoomed-out photos that show the landscape.

•Write down the location, habitat, size and density of the infestation.

•Contact one of these experts to help confirm identification:

- Extension Forestry: Email forestry@extension.wisc.edu or call Working Lands Forestry Educator Tony Johnson at 608-386-8900.

- Wisconsin DNR: Email invasive.species@wisconsin.gov.

In 2020, there was an isolated case of Japanese stiltgrass in La Crosse County, which the Department of Natural Resources is working to eradicate.

Renz said his team is using the DNR’s experiences in eradicating the plant to learn how to speed up the process.

'But it takes time, right?' Renz said. 'It’s not like you’re walking out there in this and it’s really easy to identify these plants. It’s a forest, so there’s all sorts of other plants there where this plant can be growing underneath there.

'We don’t want to harm the other plants, but we want to take this one out, so it can be quite challenging.'