Voracious, aggressive, born pregnant and highly adaptive, the Asian Crazy Worm is on the march in Maine.
It may sound like something out of a B horror movie, but the threat the invasive species represents to soil and plants is very real.
Also known as “snake worms” and “Alabama jumping worms,” the aggressive Amynthas agrestis is not the friendly, soil-enriching earthworm gardeners and farmers welcome on their land.
“These are worms that live at the surface, not the kind that go deep into the soil,” according to Gary Fish, state horticulturalist with the Maine Department of Agriculture, Conservation and Forestry. “They stay in the forest litter or top parts of the forest floor [and] can mix up the top layers of soil so much and eat so much of the organic material, the dirt looks like coffee grounds.”
A 2014 study at the University of Wisconsin published in Science Daily, showed leaf litter declined by 95 percent in areas populated by the crazy worms, which left behind “residue that was almost pebbly in consistency — grainy little balls of dirt that may make it hard for the seeds of native plants to germinate.”
That can be an issue for shallow rooted plants and trees, like sugar maples, Fish said.
“There is a definite depletion of leaf litter and rapid loss of nutrients because the [crazy worms] break them down too fast,” Fish said. “So you get this initial spike of nutrients and then sudden depletion — this is not the normal slow and steady release of nutrients and plants don’t like this sort of feast or famine.”
The crazy worms are thought to have been in Maine since the late 1800s or early 1900s, Fish said. But it was not until 2012 that an established population of the worms was confirmed in the state.
“That was when the Maine Coastal Botanical Gardens found some in a rhododendron display,” Fish said. “In 2014 another population was confirmed at the arboretum in Augusta and they have also been found in several sites in Portland.”
In ecosystems like Maine, he said, the plants and trees have evolved using nutrients broken down by native fungi — a very slow process, according to William Cullina, president and CEO of the Maine Coastal Botanical Gardens.
“It may take the fungi three years to break down a single leaf,” Cullina said. “These [crazy] worms can break down the same leaf in three weeks and the plants don’t have a chance to use the nutrients.”
There is some uncertainty where the worms came from in the first place, but Fish said they are spread within horticultural materials like potting soils or mulch and the eggs are easy to miss due to their tiny size.
“The message we really want to get out is don’t do anything that can spread them around,” Fish said. “Use soils and materials that have been sterilized or compost that has been thoroughly heated.”
According to Fish, it only takes one crazy worm to get the ball rolling.
“They are parthenogenic,” he said. “So it only takes one to start a population.”
Parthenogenesis is asexual reproduction used by some insects and invertebrates in which embryos form from unfertilized eggs. Basically, crazy worms are all born pregnant and, on top of that, tend to reproduce much faster than European earthworms.
William Cullina, president and CEO of the Coastal Maine Botanical Gardens has seen this first-hand.
“I worked in Massachusetts before coming to Maine and we had a really bad problem with them,” Cullina said. “They are really egg-laying machines that can disrupt the natural balance in an ecosystem.”
The crazy worms seem most attracted to soils with low acidity and Cullina said in the Massachusetts gardens in which he worked, when the soil pH levels fell, the worms moved in.
The natural pH levels in Maine may help prevent the spread of the worm, Fish said.
“These worms don’t like pH levels lower than 5 or 5.5,” he said. “A lot of our coniferous forests are lower — more acidic — than that.”
Cullina said the crazy worms have already had some severe impacts in the upper midwest of the US. where their activities have had detrimental effects on native woodlands and species, including birds and smaller vertebrates that rely on the plants destroyed by the worms.
Once they move into an area, Cullina and Fish said there is not much that can be done about it.
“There’s really not anything on the market that’s been found to work on them,” Fish said. “So it’s really about trying to slow the spread of them and being aware when you are moving plants and soils around there could be a danger of importing the crazy worms.”
Cullina said he has heard anecdotal stories of a flatworm from New Zealand that has been used to fight off the crazy worms.
“It’s a predator to the crazy worms that looks sort of like a tape worm,” he said. “I read there was an outbreak of crazy worms in Ireland and this flatworm got into that population and decimated it.”
Fish wants to keep track of crazy worms in Maine and asks anyone who even thinks they have them to submit any information they have to the online Maine invasive species database at www.imapinvasives.org/mainelogin.
As for the “crazy” reputation, Cullina said it’s well earned because of they will literally pop out of the ground or out from under leaves, jump and wriggle in a frantic manner.
“They kind of come out of the ground like snakes if they are disturbed and wriggle quickly across the ground,” he said. “They are pointy on both ends, very fast and can erupt out of the ground in large numbers [and] look like Medusa. I’ve seen them boil up out of the ground, it’s kind of disgusting.”
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