The writhing worm in ecologist Brad Herricks hand is still fairly new in town, but its taken only a few years for its kind to collectively damage swaths of the University of WisconsinMadison Arboretum where he works. The unassuming invertebrates first arrived to this foresta complex web of sugar maple, beech, yellow birch, and hemlock intended to mimic the states hardwood forestsin 2013, concealed in an order of mulch that carried castings of the invasive worm. Arboretum naturalists knew they were dealing with Asian jumping worms, but they had no idea how to stop them from taking over.
Until recently, these forests soils were largely wormless. During the last ice age, which ended roughly 12,000 years ago, glaciers wiped out earthworms in what is now the northern United States. Absent the wriggling decomposers, forests evolved to rely on bacteria and fungi to break down leaves and twigs that litter the floor. Earthworms found in U.S. soils today are mostly invaders from Europe, but in the last few decades more than a dozen species of jumping wormsa more destructive group from Asia used as bait or in commercial mulchhave spread. In the 1990s, scientists began documenting their damage to forests in Southern Appalachia, the Northeast, and Oregon. Now, the worms have made it to the Upper Midwest, and scientists fear the invaders will inextricably alter the regions forest floor ecosystem and harm birds that nest there.
Once let loose, jumping worm invasions are hard to contain. Where most European worm species move about 30 feet per year, jumping worms can easily cover 17 acres, or roughly the size of 13 football fields, of new ground in a single season. In Illinois, experts confirmed the presence of jumping worms, also known as Alabama jumpers, crazy worms, and snake worms, in 2015. In the past year, first reports of the worms have come out of counties in Minnesota, Iowa, and Wisconsin, and this August scientists in Chicago confirmed that jumping worms had effectively invaded the entire city.
According to Scott Loss, a conservation biologist at Oklahoma State University, the spread of jumping worms could exacerbate the impact other invasive earthworms have already had on forests in eastern and Midwest forests.
Once let loose, jumping worm invasions are hard to contain. Where most European worm species move about 30 feet per year, jumping worms can easily cover 17 acres, or roughly the size of 13 football fields, of new ground in a single season. In Illinois, experts confirmed the presence of jumping worms, also known as Alabama jumpers, crazy worms, and snake worms, in 2015. In the past year, first reports of the worms have come out of counties in Minnesota, Iowa, and Wisconsin, and this August scientists in Chicago confirmed that jumping worms had effectively invaded the entire city.
Meanwhile, scientists at the Universities of Wisconsin and Minnesota are testing the use of pesticides containing saponin, a substance that can be found in tea and maple leaves. When trying to keep worms off the green, golf course managers prefer saponin-based pesticides over more hazardous ones that are typically used in backyards. “We hope saponin can control the worms without disrupting the ecosystem because it naturally occurs in plants,” says Frelich. “We could use a lot of poisons, but they would also kill everything else.” .
According to Lee Frelich, director of the University of Minnesota Center for Forest Ecology, it is crucial to stop the invasive species from spreading, regardless of whether jumping worms would make a tasty meal for some birds. His team has discovered evidence that the worms’ success is limited in hotter and drier soils, which may slow the worms’ spread throughout his state. In order to concentrate monitoring and eradication efforts, his team will be able to predict where on the continent Asian jumping worms are most likely to spread if they can precisely measure how hot, cold, or dry the soil needs to be in order to keep the worms out.
Oklahoma State University conservation biologist Scott Loss believes that the introduction of jumping worms may worsen the effects that other invasive earthworms have already had on eastern and Midwest forests.
Until recently, these forests soils were largely wormless. During the last ice age, which ended roughly 12,000 years ago, glaciers wiped out earthworms in what is now the northern United States. Absent the wriggling decomposers, forests evolved to rely on bacteria and fungi to break down leaves and twigs that litter the floor. Earthworms found in U.S. soils today are mostly invaders from Europe, but in the last few decades more than a dozen species of jumping wormsa more destructive group from Asia used as bait or in commercial mulchhave spread. In the 1990s, scientists began documenting their damage to forests in Southern Appalachia, the Northeast, and Oregon. Now, the worms have made it to the Upper Midwest, and scientists fear the invaders will inextricably alter the regions forest floor ecosystem and harm birds that nest there.
What Are They? Jumping worm. Photo: Josef Gorres, University of Vermont
Large, plump earthworms that can grow up to 8 inches (20 cm) in length are known as jumping worms. They resemble common earthworms (Lombricus terrestris), also known as nightcrawlers or dew worms, but they have an unexpected habit of jumping and thrashing when disturbed! They are highly animated and prefer to stay on the soil’s surface. They then slither from side to side in motions more akin to snakes than worms. Regarding the moniker “crazy worms,” I believe that any earthworm that becomes agitated or jumps when disturbed is probably a little crazy.
Theyre not just present in northeastern North America. Theyve become established many other parts of the world. They go by different names in the Southeast United States, where they have been for over a century: Georgia jumpers or Alabama jumpers. A distinct group of Amynthas species appears to be involved in their rapid spread throughout Europe, where they are currently also present.
Damage Done Forest floor damaged by jumping worms. Photo: UVM
Jumping earthworms are more common than regular earthworms and move quickly through the layer of forest litter (duff), consuming it by 2095% and leaving the soil nearly bare. Other earthworm species do not exhibit this behavior. Because the litter is breaking down so quickly, the soil and plant roots are unable to fully absorb all of the released nutrients. It acts as if it were a fast-release fertilizer rather than a slow-release one, impoverishing the top soil layers, compacting the lower soil layers, and contaminating neighboring bodies of water with nitrogen and phosphorus.
Additionally, jumping worms eat plant seeds, depleting the soil seed bank’s supply. The forest floor loses a variety of plant species as a result of that and the environmental damage they create. Native plants that depend on dense leaf litter disappear, primarily to be replaced by invasive exotic weeds. They are equally damaging in forest and prairie environments.
Animals are likewise affected. After giving jumping worms a taste, salamanders and many bird species will either spit them out or avoid them. Ground-nesting birds disappear. But moles can help control them because they will eat them.
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