Crazy worms — an invasive species from Asia — pose a threat to forests, scientists say. The worms can thrash around so violently that they can jump out of a person's hand. They also lose their tail — on purpose. Josef Görres/Plant and Soil Science Department University of Vermont
Earthworms are often seen as a welcome presence in gardens, and even on fishing hooks. But in the Northeast, experts say invasive "crazy worms" from Asia are creating havoc in forests — and they say the unusual worms are a danger to animals and plants, and especially to sugar maple trees.
"The street cred that they have is hiding the invasion," Josef Görres, a soil scientist at the University of Vermont, says of the worms.
"I call earthworm invasions 'socially cryptic,' " Görres tells NPR, "because folks think of earthworms as the good guys — and maybe they are in certain ecosystems. But in the context of the northern [U.S.] forest, they are relative newcomers that have the potential to have huge effects."
Crazy worms — also known as jumper worms — reproduce rapidly. They also love to tear through the nutritious layer of decomposing leaves and nutrients that blanket the forest floor — a habit that can be very damaging to forests, including maple trees.
First things first: Why people call them crazy worms
So, what makes these worms so crazy?
"They're really active worms, and the craziness comes from that. They can jump out of your hand," Görres says, adding that the creatures' intense wriggling can launch them into the air.
"And they also lose their tails," he adds. "Some of the species will lose their tails just like a salamander. So that is kind of crazy, too, when you see it."
The worms don't regenerate a new tail — it's more like a single-use get-out-of-jail card.
"It's a one-time defense against a nasty bird that comes around to pick it up," Görres says. "It splits. The live part of the worm actually sort of slithers away, and the tail keeps thrashing about. So it is basically saying, 'Here I am, you pick me up, I'm the worm.' "
"They are very active," Monica Turner, a University of Wisconsin-Madison professor, once told Wisconsin Public Radio. "They almost seem like worms that want to be snakes."
Crazy bad, not crazy good
Although some earthworms can be helpful to gardeners, they can also cause problems in forests. And that's especially true for the Asian earthworms that are classified in the Amynthas genus.
The worms "are pretty much foes for everything," Maine State Horticulturist Gary Fish recently told Maine Public Radio.
The worms possess a slew of characteristics that make them a problem for forest managers and horticulturists. They're voracious eaters — and while most earthworms delve deep into the soil, crazy worms prefer to stay in the springy "duff" layer of decomposing organic material.
"They eat the forest duff much faster than a lot of the other European worms because they stay right in that duff, they don't go deep into the ground," Fish said. "They stay right at that duff level, and just eat it all up really fast."
Plus, they alter the composition of the soil, creating a texture that's often compared to coffee grounds. The modified soil is ruined for many native plants, as it's stripped of vital nutrients and prone to increased erosion.
The worms can even cause challenges for casual gardeners. "Homeowners may see garden plants killed and may have difficulty growing plants," Minnesota's Department of Natural Resources says.
In these images showing two stands of sugar maple trees, the one on the left has not been invaded by Asian crazy worms, and the one on the right has. Josef Görres/Plant and Soil Science Department University of Vermont
The Asian worms also have biological advantages. They can reproduce asexually, through parthenogenesis. And because they mature in just 60 days, two groups of offspring can hatch in a single season.
A number of states, including Maine and New York, have banned crazy worms outright.
What about my syrup?
Crazy worms' impact on maple syrup could be "severe," Fish told Maine Public Radio.
"They tend to really impact maple trees," he said, particularly because those trees tend to have shallow roots.
"Without that protective leaf litter and duff layer, they become very stressed, and they're more susceptible to insects and diseases, and they're less likely to grow very fast," he said.
In Vermont, Görres says that if the earthworms invade more forests there and across the border in Canada, "there's going to be a lot less regeneration of maple trees — of sugar maple in particular."
When the worms go through forests' duff layer, they also take away a crucial germination medium for small plants that usually supply food for deer. When those plants aren't abundant, Görres says, deer "will start browsing on other things, such as saplings of trees, including maples."
Delivering what he cautions is a speculative forecast, Görres says that within the next 50 to 100 years, "there'll be less and less maple syrup."
They've been crawling among us for decades
A crazy worm by any other name, it turns out, would cause just as many problems. In the South, they're sometimes called Alabama jumpers or Georgia jumpers — and they've often sold as a lively form of fish bait. In New Jersey, they're called Jersey wrigglers, Görres says. They're also known as snake worms, because of the vigorous way they move.
The forests of the Northeastern U.S. are especially vulnerable to crazy worms because of glaciation. When massive glaciers scoured the area with ice thousands of years ago, the area, like other parts of the Northern U.S., was left with no native earthworms.
Earthworms such as nightcrawlers came to the region later, arriving along with colonists from Europe. Then, in the 1800s, the new type of worms arrived from Asia. But it wasn't until fairly recently that crazy worms were seen as becoming established, and Görres and other scientists say they seem to be spreading more now.
The worms mainly spread within the U.S. through the domestic market, both through the horticulture industry and through their sale as fish bait.
Crazy worms can be identified by a few unique qualities, starting with their behavior. They also have a milky white or gray clitellum — the band that many earthworms have — that is flush with the rest of their body.
Trying to tame crazy worms
When asked what can be done to stop or slow down the worms' spread, Görres says he and his team are working on environmentally safe ideas such as using fungi or insecticidal soaps.
But he adds that it's difficult to find funding for projects to take down earthworm populations — another consequence, he said, of their street cred.
"Who would fund research on killing these worms, or figuring out how to get rid of them?" he asks.
As Wisconsin's Department of Natural Resources says, "There is no 'magic bullet' to control jumping worms, at least not yet."
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