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Rebecca Smith noticed slithering, thrashing worms inching their way up the walls of her home in Carthage, Texas, this spring. After a recent rainstorm, she found two large worms in her living room.
“They are bizarre,” Smith said. “It looks like a worm until you touch it. And then it starts freaking out like a snake would.”
Smith thought the worm was just a “crazy” earthworm but then identified it as a jumping worm -- an invasive species that’s made its way to nearly 40 states, including most of the central U.S., and most recently, Colorado.
“When we Googled it, it said to get a bucket and kill them because they are just horrible for the soil,” Smith said.
Jumping worms look nearly identical to a common earthworm, except for a thick, light-colored band near the top of their heads. But these worms damage soil in gardens and forests. And they are nearly impossible to get rid of because their tiny cocoons blend with the soil and can lay dormant for years.
The invasive species has been in the U.S. for as long as two centuries. But people have only recently started to recognize them, according to Brent Crain, a horticulture educator with Michigan State University extension.
“No one knew that they were a threat,” Crain said. “No one understood that they were invasive and just that lack of education probably resulted in a lot of underreporting.”
Gardeners across the country have come up with home remedies to try and dispel the worms, but researchers say that preventing the spread is the most efficient way to minimize their damage.
What experts know
The worms only burrow at the top of the soil, according to Brad Herrick, who’s the director of the Lakeshore Nature Preserve at the University of Wisconsin-Madison.
He said they also leave behind coffee-ground-textured waste that contributes to making soil porous and in some cases hydrophobic, which means it struggles to absorb water.
“The first indication of jumping worms is this change in what the soil looks like,” Herrick said. “If you see that, where you can just sort of wipe away the soil with your hand, that's a red flag.”
Ulric Chung, master gardener at Michigan State University Extension, said he noticed that quintessential soil right before he discovered the worms in a local garden.
“It's very crumbly, but it's not like regular garden soil, which kind of sticks together a little bit,” Chung said.
There were also signs in the plants themselves, which Chung said looked more yellow than a healthy plant should and were far too easy to pull out of the ground
The worms eat up organic matter in the top layer of soil, which makes it hard for some plants to thrive, Herrick said.
“Species that are annual, that have shallow roots, those are the ones that we expect to probably suffer in the short term because they are trying to get established in a very porous soil that's been worked over by jumping worms,” Herrick said.
Jumping worms also destroy habitats for other invertebrates and ground nesting birds, said Crain with Michigan State University Extension. That’s because they eat leaf litter and organic matter topsoil at a faster rate than earthworms.
This behavior makes it hard for seedlings to grow, especially in forests, Crain said.
“When that leaf litter is destroyed, then a lot of these smaller plants disappear too,” Crain said. “Where you used to have ferns, all of a sudden, you may not have ferns anymore… The biodiversity is destroyed and the entire forest floor ecosystem is altered.”
Crain said typical earthworms are already bad for forests, but jumping worms have a bigger appetite and don’t need a mate to reproduce.
“A single worm will begin producing cocoons, producing these eggs, and they can spread very rapidly in the area,” Crain said.
Although gardens and forests are starting to feel the effects, Herrick says jumping worms are still in the early stages of invasion.
“Sometimes it takes a while for us to see impacts over large scales,” Herrick said. “Especially for a cryptic invader like this that affects ecosystems by manipulating the soil.”
Prevention is key
Humans are a main reason that jumping worms are spreading, according to Crain. He said the best way to slow the spread is by cleaning gardening tools and tire treads.
“Those are the places that soil gets in, and wherever there's soil… you can also have the cocoons from these earthworms,” Crain said.
Mary Spies teaches gardeners in St. Louis, Missouri, about the worms. She’s part of the St. Louis chapter of the Native Plants Society.
“I take jumping worms in a baggie so that people can see them and compare them to an earthworm,” Spies said. “They can see how much more rubbery they are and how they're two-toned instead of a single tone.”
She said she completely removes the soil from plants when she gives them to others to prevent cocoons from spreading.
“You have to wash the roots off and get rid of all of the dirt,” Spies said. “These cocoons are smaller than a pinhead. You have no idea that there's not a cocoon in the dirt that's still collecting on these roots.”
Crain also recommends that fishers avoid using the worms as bait and dispose of any bait properly, rather than dumping them in the water or forests.
Buying plants locally is another way to mitigate the spread of any invasive species, according to Herrick. He recommends asking questions about where your products come from and making sure your neighbors are aware of the worm and the warning signs.
“We can't control everything obviously, but things that we can control a little bit can really help to prevent a spread,” Herrick said.
Heat may help
There’s growing research on how to deal with the worms themselves.
One study from the University of Wisconsin found that the worm’s cocoons can’t survive if they are exposed to 100 degree temperatures for three days.
Herrick recommends using steam, direct fire or creating a greenhouse effect by covering your garden with a clear plastic cover early in the season to kill off cocoons.
“That doesn't mean that they wouldn't come back the next year,” Herrick said. “But we know heat is a good control option for the cocoons.”
The University of Illinois Extension recommends picking out adult worms from the soil and leaving them in plastic bags under the sun for 10 minutes. Pouring a mixture of water and ground mustard seed on top of soil will help bring jumping worms to the surface.
Herrick said an insecticide called Botanigard uses high concentrations of naturally-occurring fungi that helps control soft-bodied pests — including jumping worms. He said it doesn’t affect cocoons, but it will deplete adult populations.
“Over time you'd see fewer and fewer cocoons being produced,” Herrick said. “In terms of control, that's a new idea for gardeners.”
Herrick said it’s best to exercise caution, even if you think you’ve gotten rid of the worms.
“What happened in a given year doesn't actually dictate what happens in the following year,” Herrick said. “If you see a real low year because of the drought, just know that it doesn't mean that they're gone forever. They're just laying in the soil, waiting for conditions to return.”
Community effort
Chung, the master gardener in Michigan, said he’s starting to accept that he may never kick the invasive species from his garden.
“The things that are good and natural for the soil are also good and natural for jumping worms too,” Chung said. “So I'm kind of becoming more resigned to the fact that we're gonna have to live with them, whatever that might mean.”
Chung said he’s considering using more native plants or planting seeds in different soil and then transplanting them into the garden.
Although dealing with the worms takes a lot of work, Spies in St. Louis said she will continue to educate local gardeners on the worm.
“We want people to have thriving gardens, but we can have thriving gardens without trading plants in pots that we've set up soil that could have jumping worms in it,” she said. “There are better ways.”
Spies said being proactive is the best way she’s found to prevent the spread in her community.
“We need to be community-minded about this and ensure that we're doing the best to take care of the resources that we have for future generations.”
This story was produced in partnership with Harvest Public Media, a collaboration of public media newsrooms in the Midwest and Great Plains. It reports on food systems, agriculture and rural issues.
