Are Invasive Jumping Worms Taking Over?
Most gardeners are thrilled when they find earthworms tunneling through their gardens. Normally, they’re a sign of rich soil, happy plants, and a bustling ecosystem. But one unwanted visitor is squirming its way into gardens and forests all across the country: the invasive jumping worm, known for its thrashing, restless behavior.
Gardeners and scientists have become more and more concerned with these worms, which can cause damage in yards and forests. They’re known for taking dense, healthy soil and churning it into a coffee ground-like mixture, which can lead to erosion and make it more challenging for plants to anchor themselves.
But it turns out that most earthworms we find in the U.S. are already invasive, and the jumping worm is just the newest one to join the party. How different is this invasive worm from the ones we’re more familiar with?
To learn more, guest host John Dankosky speaks with Bernie Williams, a plant pest and disease specialist at the Wisconsin Department of Natural Resources based in Madison, Wisconsin. They talk about how to spot these worms, what kind of damage they inflict, and just how concerned we should be.
Invest in quality science journalism by making a donation to Science Friday.
Bernie Williams is a plant pest and disease specialist with the Wisconsin Department of Natural Resources in Madison, Wisconsin.
JOHN DANKOSKY: This is Science Friday. I’m John Dankosky. Ira Flatow is away. I’m going to brag a bit here– my gardens this year are better than they’ve ever been. The flowers are in bloom. The plants and trees are all doing well. And I got to say, I’m pretty happy about it.
Now, one of the sure signs I’ve always looked for in a healthy garden is earthworms. They tell me that I’ve got soil that’s bustling with life and nutrients. But this summer, I’ve got my eye out for one worm in particular. It’s known for its thrashing, squirming, restless behavior. It’s the jumping worm.
These critters are native to eastern Asia, but they’ve been quietly spreading throughout the US for decades. Now they’re in more than 30 states, munching their way through forests and gardens. Scientists and gardeners alike are concerned about jumping worms. But just how worried do we need to be?
Here to tell us more is Bernie Williams, plant pest and disease specialist at the Wisconsin Department of Natural Resources, based in Madison, Wisconsin. Bernie, welcome to Science Friday
BERNIE WILLIAMS: Well, thank you for having me, and thank you for letting me talk about some of my favorite animals today.
JOHN DANKOSKY: Absolutely. We’re happy to have you doing this. So let’s get this out of the way first of all– the word “jumping” kind of sounds a bit terrifying. I mean, do these worms actually jump?
BERNIE WILLIAMS: I mean, I wouldn’t say that they actually jump. They thrash. They’re very active. They throw their bodies about. I think some of the best analogies that I’ve heard to describe them are people say that they dance about, which they do. It’s such an amazing creature to see.
But also, just their active behavior is something to behold. And that’s why people become very alarmed, because they see these thrashing worms. And they suddenly think, oh no, what’s that?
JOHN DANKOSKY: I’ve picked up plenty of worms in the garden over the years. And sometimes the worms thrash around a little bit, and sometimes they’re very, very gentle. Is that the difference between the jumping worm and maybe the better worm that I shouldn’t be so worried about?
BERNIE WILLIAMS: Well, the thing about worms, when you’re looking at them, you have to understand that most of the earthworms that you’re seeing, particularly if you’re along the East Coast or you’re in the upper Midwest, most of them are generally going to be non-native worms. And we have a variety pack of European earthworms. And a couple of them will actually move very actively, and people will mistake them for jumping worms.
So when you’re looking at a worm, and I’ve looked at lots of worms, European earthworms, they tend to be– I wouldn’t say spongy, but they’re not as firm. Jumping worms, they’re much more firm, active. Really, their skin is really tight. It’s almost– they’re turgid. They’re firm. They’re like a slightly overstuffed bratwurst because they’re so tight.
It’s also, when you’re looking at them visually, the clitellum, which is the reproductive area on earthworms, tends to be smooth, whereas the clitellum on European earthworms and a great deal of North American earthworms is raised. It’s a very different worm by all means.
JOHN DANKOSKY: How exactly have these jumping worms spread so far and so fast?
BERNIE WILLIAMS: They’ve been in North America well over a hundred years. It’s, with invasive species, that often they sort of hang out. They’re dormant. They’re here, but nobody notices them. And then, all of a sudden, they get this leading edge.
So the same can be said for a lot of invasives that people deal with now. So garlic mustard was pretty benign for a long time. And then all of a sudden, it was everywhere. And these worms are tending to follow that same pathway. So they’ve been here, but now people are really starting to notice them.
JOHN DANKOSKY: If I have this right, you were the first person to discover jumping worms in your state of Wisconsin?
BERNIE WILLIAMS: Well, I think there are documentations of them prior to our stumbling across them. We were doing a field trip for a conference on invasive species. And Brad Herrick, who’s the ecologist at UW Arboretum, we worked on this field trip together. And lo and behold– they had to sit through the day with boring people talking about plants and worms all day. And then we took them out at the end of the day, and lo and behold, we stumbled across all of the jumping worms out there. I like worms, so I was sort of excited. And then we got other people excited.
JOHN DANKOSKY: Were you worried about this when you found these worms?
BERNIE WILLIAMS: Well, because I had been working with invasives for so long, I was sort of– I was awestruck. So you do a little of the ooh and ah, like, ooh, a new invasive. But I mean, when you’re looking at an invasive like that and it’s a new discovery, it’s the yin and the yang.
It’s something new that, oh, now we’re going to have a problem with this. But then it’s also, well, there’s so many of them. How long have they been here, actually? So should we really sound the alarms? And I do realize that people are very concerned about these worms. But I do think that we are lacking a great deal of information on them yet to put them in that category of, oh no, the roof’s on fire.
JOHN DANKOSKY: What should we be concerned about? I mean, what damage do these worms cause?
BERNIE WILLIAMS: These worms, they move really quickly. They’re asexual reproduction, so they don’t mate, whereas European earthworms and a lot of North American earthworms, they’re hermaphrodites, but they mate. Jumping worms, they’re primed and ready to go. And they’re here for the season and they’re gone, unlike European earthworms– they could live for two years or they can live up to 10 years, whereas jumping worms are only here for a season. They’re hatching continuously. They can outcompete a lot of the European earthworms.
JOHN DANKOSKY: OK, so they’re outcompeting some of the other worms, the native worms and the European earthworms that we know here in the US. But the way that they churn through the soil actually causes problems with erosion, right?
BERNIE WILLIAMS: Well, but all worms can cause problems with erosion. I always like to remind people, keep in mind that the good worms are not native as well. And they can cause a lot of erosion as well.
What jumping worms do to the soil is they turn it over really, really quickly so it becomes porous. So it almost becomes like coffee grounds, tapioca pudding pearls. So it’s really hard for plants, trees, shrubs to sort of anchor in there. But they’re also speeding up that nutrient cycle within the soil as well. So that soil texture changes dramatically with the presence of jumping worms. But it generally hangs out in the first two inches.
JOHN DANKOSKY: The first two inches of the soil. Is that especially bad for forested areas?
BERNIE WILLIAMS: Forest is this dynamic place to begin with. And everything is happening below ground and above ground. But within a forest, you have European earthworms, which can cause a lot of damage all on their own. And then if you surmise that jumping worms are going to move in there as well, you’re going to see that cycle become faster.
And it could potentially damage a lot of things. But you also have to take into account that this is the secondary invasion of an earthworm into a native forest. So when you get one invasive in, it sort of invites another one to come in and another one to come in, and they sort of just pile up on top of one another.
JOHN DANKOSKY: I assume that they have predators. I mean, can we just count on the robins in my yard to pluck them out and eat them?
BERNIE WILLIAMS: Oh, and that’s the really cool thing about these worms. Say if you irritate them, they’ll thrash and they’ll move about. Some may even throw their tail, so shed their tail. But they also have the ability to secrete a really distasteful liquid, so almost like a secretion which says, ugh, I don’t taste good, drop me.
And so that’s why you tend to see so many of them, because a lot of animals are not predating upon them because they’re distasteful. But if you look at how invasives evolve and move, they’re going– animals are going to adapt to it, and they’re going to start feeding on them as well. But that’s a really amazing thing about these worms.
And not to say that animals aren’t eating them. I have lots of friends that have backyard chickens, and they swear that their chickens love them. So the rest of the birds just have to get on board with the chickens.
JOHN DANKOSKY: Well, and this is a hard conversation to have with someone who loves worms at their core like you do. But I don’t know, Bernie, what do we do if we find these jumping worms in our yard or in our forest?
BERNIE WILLIAMS: The first thing is not to get so incredibly upset as people have, because there’s easy ways to get on top of them. There are so many of them. You can remove them from the surface, because they generally are right there on the surface of the soil.
So they’re easy to pluck out. Put them in a Ziploc bag, you know, as you’re out there weeding. You can put them in a bucket with some water and vinegar. You can bag them. If you have them in your compost or you suspect that you have them in your compost, you can tarp it, because heat is really detrimental to them as well. So you just want to heat it up to hit at least 104 degrees.
There’s a lot of things that you can do. I don’t recommend pesticides. You can certainly kill lots of worms with pesticides, but there’s other options. But you know, definitively, we don’t have a cure-all for them. And I’m not quite sure we will.
JOHN DANKOSKY: It sounds to me, though, Bernie, like what you’re saying is that people are very concerned about this, but they maybe need not be so concerned. I mean, almost all of the worms that we’re going to find in North America are probably already invasive, right?
BERNIE WILLIAMS: A good percentage of them, yes. I’m in Wisconsin, and I’m originally from Pennsylvania. You’re along the East Coast. The probability that you have native North American earthworms in your area is 3%. There’s so few North American earthworms in this particular area of North America.
In Wisconsin, I’ve been doing worms for 20 years. I have never encountered a native North American earthworm.
JOHN DANKOSKY: When I was talking off the top of our segment about the health of my garden, and I’ve always thought that the presence of earthworms is something that is good for my soil. Am I wrong about that, Bernie? Am I getting something substantially wrong about having worms in my soil?
BERNIE WILLIAMS: No, no, not at all. No, I mean, earthworms are extremely beneficial animals. And when you look at the history of them, they provide a lot of really good things, nutrients. They turn over, they recycle everything. And they’re providing really beneficial fungal relationships in that soil and the bacteria.
It’s really important. When people get upset about worms you have to point out to them, they can be highly damaging to forests, but in urban areas, in agricultural settings, they’re really amazing earth turners. They are doing incredible things that you’ll never quite see because they’re underground. When they cause issues, it’s really when you’re looking at forests, natural areas, places that you want to preserve.
You really have to look at it big picture. That’s the way I always approach invasives. It’s not just one. It’s the combination of a bunch of them which really causes the issue.
And earthworms, they’re just the cool kid on the block right now. And everybody wants to talk about jumping worms. So it’s great that they’re getting their 15 minutes of fame.
JOHN DANKOSKY: Well, I’m glad that you were able to be here to help us talk through some of the interesting things about these jumping worms, but also some of the problems as well. Bernie Williams is a plant pest and disease specialist at the Wisconsin Department of Natural Resources, based in Madison, Wisconsin. Bernie, thanks so much.
BERNIE WILLIAMS: Oh, thank you.
John Dankosky works with the radio team to create our weekly show, and is helping to build our State of Science Reporting Network. He’s also been a long-time guest host on Science Friday. He and his wife have four cats, thousands of bees, and a yoga studio in the sleepy Northwest hills of Connecticut.