Learn how to eradicate jumping worms, what to look for to identify them, and where you might find them hitching a ride.
You may have heard of lionfish in the Atlantic Ocean and Burmese pythons in the Everglades, but another invasive species has been under our feet for over a century. Also known as “snake worms” or “crazy worms” because of their thrashing behavior, invasive Asian jumping worms comprise a group of 16 or so species that threaten our farmlands and native forests. Here’s what the experts have to say about these harmful worms.
An Emerging Problem
“I’ve been studying the group off and on for 30 years,” says Mac A. Callaham. Callaham is a research ecologist and team leader for the U.S. Forest Service at the Southern Research Station in Athens, Georgia. “It’s something that I’ve had a keen interest in for a good long time. The sad fact of this is that these worms have been present in North America for more than 100 years now.”
Asian jumping worms were first reported in California in the 1860s, and then they started appearing on the East Coast in the late 1930s and 1940s. About 10 years ago, the Arboretum at the University of Wisconsin, Madison, identified them in the state for the first time.
“They weren’t really noticed, or they weren’t really an invasive problem until the last 15 to 20 years, and that’s when they started to really move continentally,” says Brad Herrick, a research program manager and ecologist at the Arboretum.
Callaham says this continental movement means ecologists aren’t going to be able to completely banish these worms, and that the best way to control their presence is to monitor the materials we move around the planet. “These worms are really good at hitchhiking in nursery material, potted plants, or things of this nature,” he says.
At the Arboretum, Herrick and his team realized the jumping worms were more widespread than originally thought and were moving quickly. “That kicked off a whole campaign of working with the green industry here in Wisconsin to try and come up with some sort of list of best management practices that we could share with the public about how to deal with these new invasive critters.”
Currently, up to 40 states and several Canadian provinces have reported these invasive worms. Herrick’s research has found that, at their most dense, roughly 200 jumping worms can reside in one square meter of forest soil!
Effects on the Forest Ecosystem
Callaham says the biggest problem with Asian jumping worms is how they impact forested landscapes. “When they first move in as a wave of invasion, they tend to completely consume the leaf litter in the forest floor – like, down to nothing,” he explains. “This has two principal effects. [First,] you’re losing overall carbon-storage capacity, since they’re metabolizing the leaves more quickly and they’re blowing it off as carbon dioxide in respiration. The second thing, from a forest ecology standpoint, is you tend to lose a lot of the other forest-floor-related processes and organisms. Lots of animals – such as millipedes, microarthropods, and other insects that live and use that leaf litter layer as their habitat – are disappearing.”
When the jumping worms remove the layer of leaf litter, other significant effects take place in the soil structure. Their casting, burrowing, and tunneling activity all cause the soil surface to turn into a crumb structure, which can increase rates of erosion and cause water to move in different patterns.
“Soil consists of three components: chemical, biological, and physical,” Callaham says. “And these earthworms have the capacity to change all three. So, that tends to be a profound effect when they invade.”
Forests are used to detritus breaking down very slowly, and they’ve become accustomed to accumulating layers of leaves. This is important for retaining moisture and nutrients, for preventing erosion, and for germinating native plants. Leaf litter provides a habitat for arthropods, insects, amphibians, reptiles, and birds. Without the protective layer of leaf litter, other invasive animals and plants can move in more easily.
“Things such as common buckthorn and garlic mustard move in pretty quickly and displace native plants,” Herrick says. “Native plants are really taking it on the chin when [Asian jumping worms] come into their playground.”
And that’s just for starters. Since jumping worms are a relatively “new” invader, scientists are unsure of the long-term effects. “We think there’s a long-term impact on soil nutrients” in that there’s “a major decrease, potentially, in the nutrients that the soils have, which, of course, contributes to plant growth,” Herrick says. “We’re kind of learning about it as we go. They really fundamentally change an ecosystem when they move in.”
And this is just the effects the jumping worms have on a forest. The other story is how they behave in gardens.
Impacts on the Soil
The most surprising information to learn from these two experts was that in many parts of North America, there are no native earthworms.
“In the Upper Midwest, all of Canada, and the New England area, there are no native earthworms,” Herrick says. “These areas of North America experienced the last glaciation, where the glaciers had moved down, and no native earthworms survived. So, all earthworms in these areas are non-native, and many of them are invasive.”
Yet many of these non-native earthworms, such as the common night crawler, are beneficial. “They have this great ‘ecosystem service,’ where they move nutrients around the soil and they create porous soil for water to get down to the root zone,” Herrick explains.
When Asian jumping worms move in, they displace other earthworms. They can’t coexist, and the beneficial earthworms lose out by being forced to move or die. “And so you’re left with one group of earthworms that aren’t very good at moving nutrients around, since they only are working at the top layer of soil,” Herrick says. “Even hardy plants, such as hostas, tend to not be able to do very well, since the jumping worms create a granular topsoil surface. It’s hard to transplant plants into that poor soil.”
While jumping worms don’t live with beneficial earthworms, they can coexist with other species of invasive jumping worms. “For whatever reason, they like to travel together and hang out together,” Herrick says. “They’re really similar in terms of where they live in the soil and what they do.”
Identifying Jumping Worms
Rigidity. Differentiating between beneficial earthworms and invasive Asian jumping worms can be a challenge. Invasive jumping worms can be identified by their rigid bodies : They’re not as “wiggly” as beneficial earthworms. Their rigidity helps them launch out of the ground.
Clitellum. An earthworm’s clitellum is the swollen band near the “top” of its body (though it’s hard to know which end is up sometimes). The clitellum is a secretory organ that forms a cocoon for eggs. Roughly, you can use the color, size, and shape of the clitellum to identify earthworms or at least group them by family levels.
“All earthworms have a clitellum, but jumping worms have one that just kind of stands out from their body,” Herrick says. “The good earthworms’ clitellum is less distinguishable. It’s sort of three different characteristics: It’s the same coloration as their body. It doesn’t go all the way around their body (saddle shape). And on the good earthworms, the clitellum is raised, where the jumping worms’ clitellum are smooth.”
Callaham says they can still be difficult to distinguish. “In the Southeast, where I am now, we still have a good diversity of native species, so it’s really difficult to draw generalizations about how to tell them apart,” he warns. “The jumping worms have a clitellum that goes all the way around, but some of our natives have that as well.”
Still, the clitellum is a pretty good indicator of what you’re looking at. Callaham notes that most of the jumping worms have pigmentation on the clitellum, which can be greenish, brown, white, pink, or almost purple. Most of the native species in the Southeast are unpigmented and pale.
Behavior. The problem with generalizations is that there are over 100 named earthworm species in North America, with more being discovered. According to Callaham, an even better way to identify Asian jumping worms is through their behavior. Most of our native species live in mineral soil, whereas the invasive ones will be flopping around on the soil surface.
Next Steps
“Jumping worms are an annual species and depend fully on cocoons [to survive] the winter,” Herrick says. “Up in Wisconsin, we’ve gotten some hard freezes, and most of the jumping worms are probably dead, but their cocoons are overwintering.”
This is concerning, because the jumping worms are likely going to be more cold-hardy than other species. This may be even worse in warmer states, where the jumping worms may be able to live for longer periods and continue laying eggs.
You can estimate how bad your jumping worm population is by counting them. “We use a really low-cost, low-tech method called the ‘mustard extraction technique,'” Herrick explains. He mixes about 1/3 cup of mustard powder with 1 gallon of water and then pours it over the soil. As the solution infiltrates the soil profile, it’ll come in contact with the earthworms, who don’t like spicy mustard. They’ll burrow vertically to get out of the soil. While the mustard solution is a skin irritant, it doesn’t kill the worms.
How to Eradicate Jumping Worms
The best way to reduce the likelihood of Asian jumping worms on your homestead is by not spreading contaminated mulch, compost, or other horticultural materials, which is much easier said than done.
“People who really are into gardening have this habit of trading stuff and moving things around,” Callaham says. “When I bought some blueberry plants and brought them to my house, they were in a pot, and in the bottom of that pot was one of these jumping worms. And importantly, it only takes one. Just one worm can establish a whole population.”
Herrick agrees that keeping an eye out is important. “Just like in the medical field, prevention is the best medicine when it comes to invasive species,” he says. “There’s no real great technique to remove them over a large area. The only thing that we know that works for sure is heat.”
Controlled Burn
That’s where prescribed fire comes in, and Callahn says it “seems to have some limited promise. Our study was very small-scale and not done really at an operational scale.”
Callaham suggests that if you have some high-value conservation woods or forested land, you might want to consider a prescribed fire.
“First of all, you expose the cocoons to heat, which isn’t good for them. And there’s been a good bit of work on the heat tolerances of the cocoon stage. Second of all, you burn up all the food resources that they would be using for the next generation,” Callaham says.
The combination of these two factors can drive the populations down. However, almost no one is doing that, Callaham says. He doesn’t think prescribed fire would harm native earthworms, since most of them live belowground and wouldn’t be affected by the heat or the loss of leaf litter.
Soil Solarization
Herrick says that for small areas, you could try to solarize the soil, although this can also kill the good microbes and other beneficials in the soil. Exposing jumping worms and their cocoons to 104 degrees Fahrenheit for three or more days will kill them. “But we’re thinking about ways of how to implement these heat techniques on a large scale. Right now, solarization is probably the easiest to do if you have the right kind of open property that doesn’t have a lot of tree canopy and you get intense sun in the spring.”
But it all comes back to prevention. Callaham concludes, “The biggest thing is to just be really vigilant about what you move.” He also notes that “these worms are pretty widespread already and moving on their own. I don’t think it’s something that you should panic about, necessarily.”
Kenny Coogan earned a master’s degree in global sustainability and has published over 400 articles on pets, livestock, and gardening. He lives on a 1-acre homestead with a flock of Pekin ducks, and he also runs a successful carnivorous plant nursery in Tampa, Florida. Listen to Coogan co-host the “Mother Earth News and Friends”.
