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UW–Madison Arboretum ecologist Brad Herrick displays jumping worms that surfaced to escape irritating mustard poured on the soil. The worms have invaded southern Wisconsin and are thought to damage soil ecosystems.

There’s no known way to eradicate the invasive species called “jumping worms” when they make their way into a large area, a UW-Madison Arboretum ecologist said, but there also isn’t definitive proof that the worms would harm local vegetation.

For two years, Arboretum ecologist Brad Herrick, along with Nelson Institute for Environmental Studies master’s student Katie Laushman and botany professor Sara Hotchkiss, studied the effects of the jumping worms, a species of earthworm from Asia that was first identified in the Arboretum in 2013. Their study was published in the Dec. 21 issue of “Biological Invasions.”

To coax out all worms in the research area, the team poured an irritating mustard tea on the ground and identified the worms that came to the surface.

Herrick said there hasn’t been a notable change in the plant life in the area where the jumping worms were found.

“It’s a relatively new invasion, so I want to be cautious making these conclusions,” Herrick said about the dangers to habitat the worms could pose. “It could be that they’re not going to have an impact to our forest, but (damage) could be found 10 years from now.”

Herrick said he will continue monitoring the worms and their effect on the vegetation in the coming years.

Herrick and his team did find that the number of jumping worms significantly increased from one year to the next, and fewer of the European species could be found.

“There’s something going on when the jumping worms move into an area,” Herrick said. “Other European species move out, are killed or are displaced in some way.”

Research on jumping worms, which are known to change the texture and makeup of soil, is limited relating to vegetation in the Midwest, Herrick said, because the worms haven’t been in the region for many years. That’s one of the reasons he was interested in the research.

“Unless you start monitoring these sorts of things from the beginning, you won’t pick up on the environmental changes,” Herrick said.

The Arboretum has taken steps to stem the spread of the worms. Researchers were required to wash any shoes, tools or equipment used when leaving the site to prevent the worms’ tiny cocoons from dropping in other areas.

The annual plant sale has also undergone some changes, he said. Area residents cannot bring plants from their own yards, to protect against cocoons that may be in gardeners’ plots.

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Shelley K. Mesch is a general assignment reporter for the Wisconsin State Journal. She earned a degree in journalism from DePaul University.